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  • 1.
    Akansel, Serkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kumar, Ankit
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Behera, Nilamani
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Husain, Sajid
    Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Chaudhary, Sujeet
    Thin Film Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thickness dependent enhancement of damping in Co2FeAl/β-Ta thin films2018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 13, article id 134421Article in journal (Refereed)
    Abstract [en]

    In the present work Co2FeAl (CFA) thin films were deposited by ion beam sputtering on Si (100) substrates at the optimized deposition temperature of 300°C. A series of CFA films with different thickness (tCFA ); 8, 10, 12, 14, 16, 18 and 20 nm were prepared and all samples were capped with a 5 nm thick b-Ta layer. The thickness dependent static and dynamic properties of the films were studied by SQUID magnetometry, in-plane as well as out-of-plane broadband VNA-FMR measurements and angle dependent cavity FMR measurements. The saturation magnetization and the coercive field were found to be weakly thickness dependent and lie in the range 900 – 950 kA/m and 0.53 – 0.87 kA/m, respectively. The effective damping parameter ( αeff) extracted from in-plane and out-of-plane FMR results reveal a 1/tCFA dependence, the values for the in-plane αeff being larger due to two-magnon scattering (TMS). The origin of the αeff thickness dependence is spin pumping into the non-magnetic b-Ta layer and in case of the in-plane  αeff also a thickness dependent TMS contribution. From the out-of-plane FMR results, it was possible to disentangle the different contributions to αeff   and to the extract values for the intrinsic Gilbert damping (αG ) and the effective spin-mixing conductance (g_eff^↑↓ ) of the CFA/ b-Ta interface, yielding αG=1.1X10-3 and g_eff^↑↓=2.90x1019 m-2.

  • 2.
    Akansel, Serkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kumar, Ankit
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Venugopal, Vijayaharan A.
    Seagate Technol, Londonderry BT48 0BF, North Ireland.
    Esteban-Puyuelo, Raquel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Banerjee, Rudra
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Autieri, Carmine
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Behera, Nilamani
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Sortica, Mauricio A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Basu, Swaraj
    Seagate Technol, Londonderry BT48 0BF, North Ireland.
    Gubbins, Mark A.
    Seagate Technol, Londonderry BT48 0BF, North Ireland.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Enhanced Gilbert damping in Re-doped FeCo films: Combined experimental and theoretical study2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 17, article id 174408Article in journal (Refereed)
    Abstract [en]

    The effects of rhenium doping in the range 0-10 at.% on the static and dynamic magnetic properties of Fe65Co35 thin films have been studied experimentally as well as with first-principles electronic structure calculations focusing on the change of the saturation magnetization (M-s) and the Gilbert damping parameter (alpha). Both experimental and theoretical results show that M-s decreases with increasing Re-doping level, while at the same time alpha increases. The experimental low temperature saturation magnetic induction exhibits a 29% decrease, from 2.31 to 1.64 T, in the investigated doping concentration range, which is more than predicted by the theoretical calculations. The room temperature value of the damping parameter obtained from ferromagnetic resonance measurements, correcting for extrinsic contributions to the damping, is for the undoped sample 2.1 x 10(-3), which is close to the theoretically calculated Gilbert damping parameter. With 10 at.% Re doping, the damping parameter increases to 7.8 x 10(-3), which is in good agreement with the theoretical value of 7.3 x 10(-3). The increase in damping parameter with Re doping is explained by the increase in the density of states at the Fermi level, mostly contributed by the spin-up channel of Re. Moreover, both experimental and theoretical values for the damping parameter weakly decrease with decreasing temperature.

  • 3.
    Akansel, Serkan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Venugopal, Vijayaharan
    Kumar, Ankit
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gupta, Rahul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    George, Sebastian
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Neagu, Alexandra
    Tai, Cheuk-Wai
    Gubbins, Mark
    Andersson, Gabriella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Effect of seed layers on dynamic and static magnetic properties of Fe65Co35 thin films2018In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, no 30, article id 305001Article in journal (Refereed)
    Abstract [en]

    Fe65Co35 thin films have been deposited on SiO2 substrates using sputtering technique with different choices of seed layer; Ru, Ni82.5Fe17.5, Rh, Y and Zr. Best soft magnetic properties were observed with seed layers of Ru, Ni82.5Fe17.5 and Rh. Adding these seed layers, the coercivity of the Fe65Co35 films decreased to values of around 1.5 mT, which can be compared to the value of 12.5 mT obtained for films deposited without seed layer. Further investigations were performed on samples with these three seed layers in terms of dynamic magnetic properties, both on as prepared and annealed samples, using constant frequency cavity and broadband ferromagnetic resonance measurements. Damping parameters of around 8.0X10-3 and 4.5X10-3 were obtained from in-plane and out-of-plane measurements, respectively, for as prepared samples, values that were reduced to 6.5X10-3 and 4.0X10-3 for annealed samples.

  • 4.
    Bejhed Stjernberg, Rebecca
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Tian, Bo
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Eriksson, Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Oscarsson, Sven
    Stockholm Univ, Arrhenius Lab, Dept Organ Chem, SE-10691 Stockholm, Sweden..
    Strömberg, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Magnetophoretic Transport Line System for Rapid On-Chip Attomole Protein Detection2015In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, no 37, p. 10296-10302Article in journal (Refereed)
    Abstract [en]

    A lab-on-a-chip traveling wave magnetophoresis approach for sensitive and rapid protein detection is reported. In this method, a chip-based magnetic microarray comprising lines of micrometer-sized thin film magnetic elements was used to control the movement of magnetic beads (MBs). The MBs and the chip were functionalized, forming a sandwich-type assay. The MBs were transported across a detection area, and the presence of target molecules resulted in the immobilization of MBs within this area. Target quantification was accomplished by MB counting in the detection area using an optical microscope. In order to demonstrate the versatility of the microarray, biotinylated antiavidin was selected as the target protein. In this case, avidin-functionalized MBs and an avidin-functionalized detection area were used. With a total assay time of 1 to 1.5 h (depending on the labeling approach used), a limit of detection in the attomole range was achieved. Compared to on-chip surface plasmon resonance biodetection systems, our method has a larger dynamic range and is about a factor of 500 times more sensitive. Furthermore, our MB transportation system can operate in any chip-based biosensor platform, thereby significantly improving traditional biosensors.

  • 5.
    Brucas, Rimantas
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics III. Physics IV.
    Hafermann, H.
    Kastnelson, Mikhail
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics III. Physics IV.
    Soroka, Inna
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics III. Physics IV.
    Eriksson, Olle
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics III. Physics IV.
    Hjörvarsson, Björgvin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics III. Physics IV.
    Magnetization and domain structure of bcc Fe81Ni19/Co (001) superlattices2004In: Physical Review, Vol. B 69 (6), p. 064411-Article in journal (Refereed)
  • 6.
    Brucas, Rimantas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hanson, M.
    Apell, P.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, R.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Materials Science.
    Tunneling and charging effects in discontinuous superparamagnetic Ni81Fe19/Al2O3 multilayers2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 22, p. 224437-Article in journal (Refereed)
    Abstract [en]

    The magnetic and transport properties of films based on discontinuous layers of Ni81Fe19 (Py) embedded in Al2O3 were investigated. In films with nominal Py thicknesses 6 and 8 angstrom superparamagnetic particles with median diameters D-med = 2.8 and 3.1 nm and distribution widths sigma(D)= 1.2 and 1.3 nm were formed. Current voltage (IU) curves were measured with the current perpendicular to the film plane. The analyses show that the charge transport occurs via tunneling; with the charging energy supplied by thermal fluctuations at high temperature, T >= 100 K, and by the electric field at low temperature, T < 10 K. The separation of the two regimes allows independent estimates of the mean charging energy < EC > approximate to 40 meV for both samples; from the resistance R versus T analyzed in an effective-medium model at high temperature and from I versus U at 4 K. In order to obtain a consistent description of the transport properties, the size distributions must be included to account for the deviation from the single size behavior R similar to exp(E-C/k(B)T) at high T. The scaling parameter in the relation I proportional to (U/U-th-1)(gamma), where U-th is the threshold for conduction, is estimated to gamma approximate to 2 at 4 K. The superparamagnetic relaxation of the particles becomes blocked below a temperature T approximate to 20 K respective 30 K for 6 and 8 angstrom. The magnetic field (B) dependence of the resistance R(B) displays a single maximum of the ratio MR = [R(B)-R(2 T)]/R(2 T) in zero field at room temperature and a characteristic splitting of the peak at 4 K, attributed to the blocking. The maxima, approximate to 0.9% for 6 angstrom and 1.1% for 8 angstrom, are positioned at fields about a factor of two to three higher than the coercive fields of the samples.

  • 7.
    Ciuciulkaite, Agne
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Östman, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kumar, Ankit
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Verschuuren, Marc A.
    Philips Res Labs, High Tech Campus 4, Eindhoven, Netherlands.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Kapaklis, Vassilios
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Collective magnetization dynamics in nanoarrays of thin FePd disks2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 18, article id 184415Article in journal (Refereed)
    Abstract [en]

    We report on the magnetization dynamics of a square array of mesoscopic disks, fabricated from an iron palladium alloy film. The dynamics properties were explored using ferromagnetic resonance measurements and micromagnetic simulations. The obtained spectra exhibit features resulting from the interactions between the disks, with a clear dependence on both temperature and the direction of the externally applied field. We demonstrate a qualitative agreement between the measured and calculated spectra. Furthermore, we calculated the mode profiles of the standing spin waves excited during time-dependent magnetic field excitations. The resulting maps confirm that the features appearing in the ferromagnetic resonance absorption spectra originate from the temperature- and directional-dependent interdisk interactions.

  • 8.
    Flovik, Vegard
    et al.
    Norwegian Univ Sci & Technol, Dept Phys, N-7491 Trondheim, Norway..
    Macia, Ferran
    Univ Barcelona, Dept Fis Fonamental, Grp Magnetisme, E-08007 Barcelona, Spain..
    Hernandez, Joan Manel
    Univ Barcelona, Dept Fis Fonamental, Grp Magnetisme, E-08007 Barcelona, Spain..
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hanson, Maj
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Wahlstrom, Erik
    Norwegian Univ Sci & Technol, Dept Phys, N-7491 Trondheim, Norway..
    Tailoring the magnetodynamic properties of nanomagnets using magnetocrystalline and shape anisotropies2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 10, article id 104406Article in journal (Refereed)
    Abstract [en]

    Magnetodynamical properties of nanomagnets are affected by the demagnetizing fields created by the same nanoelements. In addition, magnetocrystalline anisotropy produces an effective field that also contributes to the spin dynamics. We show how the dimensions of magnetic elements can be used to balance crystalline and shape anisotropies, and that this can be used to tailor the magnetodynamic properties. We study ferromagnetic ellipses patterned from a 10-nm-thick epitaxial Fe film with dimensions ranging from 50x150 to 150x450 nm. The study combines ferromagnetic resonance (FMR) spectroscopy with analytical calculations and micromagnetic simulations, and proves that the dynamical properties can be effectively controlled by changing the size of the nanomagnets. We also show how edge defects in the samples influence the magnetization dynamics. Dynamical edge modes localized along the sample edges are strongly influenced by edge defects, and this needs to be taken into account in understanding the full FMR spectrum.

  • 9.
    Hanson, Maj
    et al.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Domain walls in Fe(001) bicrystals-thickness dependence and field-induced transitions2007In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: Magnetic domain walls (DW's) formed at the grain boundary (GB) of epitaxial bicrystal Fe(001) films, thickness t=50 and 70nm, were studied by magnetic force microscopy. The “as-grown” samples displayed DW's with different magnetic contrast profiles yielding a single peak for t=50nm and a double peak with a change of sign at the centre of the wall for t=70nm. For t=50nm the wall is characterised as an asymmetric Bloch wall. The double peak of the 70nm thick film transformed into a single peak characteristic for a charged wall, when a field of 30mT was applied along the GB. At remanence this domain wall relaxed to a regular Bloch wall divided into segments of alternating signs.

    Article · Mar 2007 · Journal of Magnetism and Magnetic Materials

  • 10.
    Hanson, Maj
    et al.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden..
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Antosiewicz, Tomasz J.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden.;Univ Warsaw, Ctr New Technol, PL-02097 Warsaw, Poland..
    Dumas, Randy K.
    Univ Gothenburg, Dept Phys, SE-41296 Gothenburg, Sweden..
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Flovik, Vegard
    Norwegian Univ Sci & Technol, Dept Phys, N-7491 Trondheim, Norway..
    Wahlstrom, Erik
    Norwegian Univ Sci & Technol, Dept Phys, N-7491 Trondheim, Norway..
    Arrays of elliptical Fe(001) nanoparticles: Magnetization reversal, dipolar interactions, and effects of finite array sizes2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 9, article id 094436Article in journal (Refereed)
    Abstract [en]

    The magnetic properties of arrays of nanoparticles are determined by the interplay between the individual particle properties and the dipolar interactions between them. Here we present a study of arrays of elliptical Fe(001) particles of thickness 10-50 nm. The aspect ratios of the ellipses are 1:3, their short axes a = 50, 100, or 150 nm, and the periodicity of the rectangular arrays is either two or four times the corresponding axes of the ellipses. Magnetic measurements together with numerical and micromagnetic calculations yield a consistent picture of the arrays, comprising single-domain nanoparticles. We show that the magnetization reversal, occurring in the range 100-400 mT for fields applied along the long axis, is mainly determined by the properties of the corresponding single Fe ellipses. The interaction fields of the order of tens of mT can be tuned by the array configurations. For the actual arrays the interactions promote switching. For film thicknesses below the Bloch wall width parameter of Fe, l(w) = 22 nm, magnetization reversal occurs without formation of domain walls or vortices. Within this range arrays may be tuned to obtain a well-defined switching field. Two general conclusions are drawn from the calculations: the character of the interaction, whether it promotes or delays magnetization reversal, is determined by the aspect ratio of the array grid, and the interaction strength saturates as the size of the array increases.

  • 11.
    Hanson, Maj
    et al.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kazakova, O.
    Effects of size and interactions on the magnetic behaviour of elliptical (001)Fe nanoparticles2007In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: Arrays of elliptical particles with aspect ratio 1:3 and short axes 50, 100 and 150 nm were prepared by electron-beam lithography and ion-beam milling of epitaxial (0 0 1)Fe films of thicknesses 10 and 20 nm. The domain state of an individual particle imaged by magnetic force microscopy in zero field after demagnetization was observed to change from being bi-domain or multidomain (MD) to stable single domains (SD) as the lateral size and film thickness were decreased. The critical size for SD formation was found to be close to the actual lateral sizes of 100 nm×300 nm and 150 nm×450 nm for the thicknesses of 20 and 10 nm, respectively. Only in the 10 nm thick ellipses of lateral size 100 nm×300 nm, the magnetization reversal may take place through coherent rotation. For all other investigated samples, the experimental switching field is lower than what would be required for this process.

    Article · Sep 2007 · Journal of Magnetism and Magnetic Materials

  • 12.
    Hanson, Maj
    et al.
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kazakova, O.
    Effects of size and interactions on the magnetic behaviour of elliptical (001)Fe nanoparticles2007In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766Article in journal (Refereed)
  • 13. Kravtsov, E.
    et al.
    Nefedov, A.
    Radu, F.
    Remhof, A.
    Zabel, H.
    Brucas, Rimantas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics III.
    Hjörvarsson, Björgvin
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics. Department of Physics and Materials Science, Physics III.
    Hoser, A.
    Wilkins, S. B.
    Proximity effect of vanadium on spin-density-wave magnetism in Cr films2004In: Physical Review, Vol. B 70, no 5, p. 054425-Article in journal (Refereed)
  • 14.
    Kumar, Ankit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Akansel, Serkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Stopfel, Henry
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Fazlali, M.
    Univ Gothenburg, Dept Phys, SE-41296 Gothenburg, Sweden..
    Åkerman, J.
    Univ Gothenburg, Dept Phys, SE-41296 Gothenburg, Sweden..
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Spin transfer torque ferromagnetic resonance induced spin pumping in the Fe/Pd bilayer system2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 6, article id 064406Article in journal (Refereed)
    Abstract [en]

    Inconsistencies in estimates of the spin Hall angle (theta(SH)) and spin diffusion length (lambda(SD)) of nonmagnetic (NM) layers using the spin transfer torque ferromagnetic resonance (ST-FMR) in ferromagnetic FM/NM bilayer structures are attributed to the inverse spin Hall effect (ISHE) and interfacial parameter contributions, interface spin transparency, interfacial anisotropic magnetoresistance, and effective spin-mixing conductance. These contributions in Fe(10 nm)/Pd(2-8 nm) bilayer structures have been probed employing the simultaneous detection of ST-FMR and ISHE in conjunction with in-plane FMR measurements. The interfacial contributions are found to increase with an increase in Pd layer thickness (t(NM)), which can be linked to the spin pumping effect in conjunction with spin backflow. Correcting the t(NM) dependence of the ST-FMR spectra for the interfacial and ISHE contributions prior to estimating theta(SH) and theta(SD) of the Pd layer, the estimated values are found to be 0.10 +/- 0.03 and 5.4 +/- 1.2 nm, respectively.

  • 15.
    Kumar, Ankit
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Wetterskog, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Lewin, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
    Tai, Cheuk-Wai
    Department of Materials and Environmental Chemistry, Stockholm University, Stockholm, Sweden.
    Akansel, Serkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Husain, Sajid
    Department of Physics, Indian Institute of Technology Delhi, New Delhi, India.
    Edvinsson, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Chaudhary, Sujeet
    Department of Physics, Indian Institute of Technology Delhi, New Delhi, India.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Effect of in situ electric-field-assisted growth on antiphase boundaries in epitaxial Fe3O4 thin films on MgO2018In: Physical Review Materials, ISSN 2475-9953, Vol. 2, no 5, article id 054407Article in journal (Refereed)
    Abstract [en]

    Antiphase boundaries (APBs) normally form as a consequence of the initial growth conditions in all spinel ferrite thin films. These boundaries result from the intrinsic nucleation and growth mechanism, and are observed as regions where the periodicity of the crystalline lattice is disrupted. The presence of APBs in epitaxial films of the inverse spinel Fe3O4 alters their electronic and magnetic properties due to strong antiferromagnetic (AF) interactions across these boundaries. We explore the effect of using in-plane in situ electric-field-assisted growth on the formation of APBs in heteroepitaxial Fe3O4(100)/MgO(100) thin films. The electric-field-assisted growth is found to reduce the AF interactions across APBs and, as a consequence, APB-free thin-film-like properties are obtained, which have been probed by electronic, magnetic, and structural characterization. The electric field plays a critical role in controlling the density of APBs during the nucleation process by providing an electrostatic force acting on adatoms and therefore changing their kinetics. This innovative technique can be employed to grow epitaxial spinel thin films with controlled AF interactions across APBs.

  • 16.
    Muscas, Giuseppe
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Theory. Uppsala Univ, Dept Phys & Astron, POB 516, SE-75120 Uppsala, Sweden.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jönsson, Petra E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Bringing nanomagnetism to the mesoscale with artificial amorphous structures2018In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, no 17, article id 174409Article in journal (Refereed)
    Abstract [en]

    In the quest for materials with emergent or improved properties, an effective route is to create artificial superstructures. Novel properties emerge from the coupling between the phases, but the strength of this coupling depends on the quality of the interfaces. Atomic control of crystalline interfaces is notoriously complicated and to elude that obstacle, we suggest here an all-amorphous design. Starting from a model amorphous iron alloy, we locally tune the magnetic behavior by creating boron-doped regions by means of ion implantation through a lithographic mask. This process preserves the amorphous environment, creating a non-topographic magnetic superstructure with smooth interfaces and no structural discontinuities. The absence of inhomogeneities acting as pinning centers for the magnetization reversal is demonstrated by the formation of magnetic vortexes for ferromagnetic disks as large as 20 mu m in diameter embedded within a paramagnetic matrix. Rigid exchange coupling between two amorphous ferromagnetic phases in a microstructured sample is evidenced by an investigation involving first-order reversal curves. The sample consists of a soft matrix with embedded elements constituting a hard phase where the anisotropy originates from an elongated shape of the elements. We provide an intuitive explanation for the micrometer-range exchange coupling mechanism and discuss how to tailor the properties of all-amorphous superstructures.

  • 17.
    Russell, Camilla
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular tools.
    Welch, Ken
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Jarvius, Jonas
    Cai, Yixiao
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nikolajeff, Fredrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Nilsson, Mats
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Immunology, Genetics and Pathology, Molecular tools.
    Gold Nanowire Based Electrical DNA Detection Using Rolling Circle Amplification2014In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 8, no 2, p. 1147-1153Article in journal (Refereed)
    Abstract [en]

    We present an electrical sensor that uses rolling circle amplification (RCA) of DNA to stretch across the gap between two electrodes, interact with metal nanoparticle seeds to generate an electrically conductive nanowire, and produce electrical signals upon detection of specific target DNA sequences. RCA is a highly specific molecular detection mechanism based on DNA probe circularization. With this technique, long single-stranded DNA with simple repetitive sequences are produced. Here we show that stretched RCA products can be metalized using silver or gold solutions to form metal wires. Upon metallization, the resistance drops from T Omega to k Omega for silver and to Omega for gold. Metallization is seeded by gold nanoparticles aligned along the single-stranded DNA product through hybridization of functionalized oligonucleotides. We show that combining RCA with electrical DNA detection produces results in readout with very high signal-to-noise ratio, an essential feature for sensitive and specific detection assays. Finally, we demonstrate detection of 10 ng of Escherichia coli genomic DNA using the sensor concept.

  • 18. Saxegaard, Magne
    et al.
    Yang, DeZheng
    Wahlström, Erik
    Norwegian Univ Sci & Technol, Dept Phys, N-7491 Trondheim, Norway.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hanson, Maj
    Chalmers, Dept Appl Phys, SE-41296 Gothenburg, Sweden.
    Field and current-induced magnetization reversal studied through spatially resolved point-contacts2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 107, no 10, p. 103909-Article in journal (Refereed)
    Abstract [en]

    ABSTRACT: We present results from scanning tunneling microscopy based point-contact measurements of the local resistance in octagon shaped, Co (20 nm )/ Cu (5 nm )/ Fe <sub>19</sub> Ni <sub>81</sub>(2.5 nm ) spin-valve rings. Through this technique one can detect the magnetoresistance with spatial resolution, and link it to magnetic domain wall motion within the ring. Measurements with varying currents indicate current-induced effects leading to offsets in the magnetic fields required for magnetic switching. The offsets can be attributed to current-induced spin-transfer torque effects for the thin Fe <sub>19</sub> Ni <sub>81</sub> layer and to Oersted field effects for the thick Co layer.

    Full-text · Article · Jun 2010 · Journal of Applied Physics

  • 19.
    Warnatz, Tobias
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Skovdal, Björn Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Magnus, Fridrik
    Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland.
    Stopfel, Henry
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Primetzhofer, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Stein, Aaron
    Center for Functional Nanomaterials, Brookhaven National Laboratory, Upton, New York 11973, USA.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    The influence of diameter on the magnetic saturation in Fe 84 Cu 16 /MgO [001] multilayered islands2020In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 496, article id 165864Article in journal (Refereed)
    Abstract [en]

    The saturation field of circular islands, consisting of [Fe84Cu16/MgO]9Fe84Cu16 multilayers, increases with decreasing diameter of the islands. When the diameter of the islands is below 450 nm the field induced changes are dominated by a coherent rotation of the moment of the Fe84Cu16 layers. For diameters of 2 μm and larger, a signature of domain nucleation and evolution is observed. The changes in the saturation field with diameter of the islands are ascribed to the interplay between interlayer exchange coupling, stray field coupling at the edges and the crystalline anisotropy of the Fe84Cu16 layers.

    The full text will be freely available from 2020-09-21 00:00
  • 20.
    Wei, Yajun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Akansel, Serkan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Thersleff, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Harward, Ian
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Ranjbar, Mojtaba
    Jana, Somnath
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Lansåker, Pia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pogoryelov, Yevgen
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Dumas, Randy K.
    Leifer, Klaus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Akerman, Johan
    Celinski, Zbigniew
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Exponentially decaying magnetic coupling in sputtered thin film FeNi/Cu/FeCo trilayers2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 4, article id 042405Article in journal (Refereed)
    Abstract [en]

    Magnetic coupling in trilayer films of FeNi/Cu/FeCo deposited on Si/SiO2 substrates have been studied. While the thicknesses of the FeNi and FeCo layers were kept constant at 100 angstrom, the thickness of the Cu spacer was varied from 5 to 50 angstrom. Both hysteresis loop and ferromagnetic resonance results indicate that all films are ferromagnetically coupled. Micromagnetic simulations well reproduce the ferromagnetic resonance mode positions measured by experiments, enabling the extraction of the coupling constants. Films with a thin Cu spacer are found to be strongly coupled, with an effective coupling constant of 3 erg/cm(2) for the sample with a 5 angstrom Cu spacer. The strong coupling strength is qualitatively understood within the framework of a combined effect of Ruderman-Kittel-Kasuya-Yosida and pinhole coupling, which is evidenced by transmission electron microscopy analysis. The magnetic coupling constant surprisingly decreases exponentially with increasing Cu spacer thickness, without showing an oscillatory thickness dependence. This is partially connected to the substantial interfacial roughness that washes away the oscillation. The results have implications on the design of multilayers for spintronic applications.

  • 21.
    Wei, Yajun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Celinski, Zbigniew
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Positive correlation between coercivity and ferromagnetic resonance extrinsic linewidth in FeCoV/SiO2 films2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, no 7, p. 072404-Article in journal (Refereed)
    Abstract [en]

    Dynamic magnetic properties of Fe49Co49V2 thin films grown on Si/SiO2 substrates have been studied by using ferromagnetic resonance technique. The effective Lande g-factor, extrinsic linewidth, and Gilbert relaxation rate are all found to decrease in magnitude with increasing sample growth temperature from 20 degrees C to about 400-500 degrees C and then on further increase of the growth temperature to increase in magnitude. Samples grown at about 400-450 degrees C display the smallest coercivity, while the smallest value of the Gilbert relaxation rate of about 0.1 GHz is obtained for samples grown at 450-500 degrees C. An almost linear relation between extrinsic linewidth and coercivity is observed, which suggests a positive correlation between magnetic inhomogeneity, coercivity, and extrinsic linewidth. The Gilbert relaxation is found to decrease with increasing lattice constant, which is ascribed to the degree of structural order in the films.

  • 22.
    Wei, Yajun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Gunnarsson, Klas
    Harward, I.
    Celinski, Z.
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Static and dynamic magnetic properties of bcc Fe49Co49V2 thin films on Si(100) substrates2013In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 46, no 49, p. 495002-Article in journal (Refereed)
    Abstract [en]

    Thin films of Fe49Co49V2 have been grown on Si(1 0 0) substrates by dc magnetron sputtering varying the substrate temperature in the range from room temperature (RT) to 600 degrees C. The static magnetic properties of the films were studied using a superconducting quantum interference device and magneto-optic Kerr effect magnetometry, while x-ray diffraction and reflectivity measurements have been used for the evaluation of the structural properties and thickness of the prepared samples. The easy axis coercivity decreases from 60 Oe for the sample grown at RT to 15 Oe for the one grown at 400 degrees C. We also studied the dynamic magnetic properties of the samples by using the high-frequency vector network analyser ferromagnetic resonance (FMR) technique. Results from FMR measurements show that the extrinsic linewidth decreases with increasing growth temperature up to 450 degrees C and then increases with further increase of growth temperature. The source of the extrinsic linewidth is two-magnon scattering by small, weak inhomogeneities. The intrinsic Gilbert damping (alpha) follows a similar trend to the extrinsic linewidth, with the lowest damping constant alpha approximate to 0.005 found at a growth temperature of 450 degrees C.

  • 23.
    Wei, Yajun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Jana, Somnath
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Brucas, Rimantas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pogoryelov, Yevgen
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Ranjbar, Mojtaba
    Arena, Dario A
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Dumas, Randy K
    Warnicke, Peter
    Johan, A
    Svedlindh, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Magnetic coupling in asymmetric FeCoV / Ru / FeNi trilayers2014In: Journal of Applied Physics, Vol. 115, no 17, p. 17D129-Article in journal (Refereed)
    Abstract [en]

    We have investigated the magnetic anisotropy and interlayer coupling in trilayer films of permendur(100 \AA)/Ru/permalloy(100 \AA), with the thickness of the Ru spacer varying from 0 to 200 \AA. While the permendur/permalloy sample exhibits a small in-plane uniaxial magnetic anisotropy with Hu = 27 Oe, all trilayers are magnetically isotropic in-plane. Results from hysteresis loop and ferromagnetic resonance measurements were fitted to a micromagnetic model, with the results indicating that all the films are ferromagnetically coupled except the one with 10 \AA Ru spacer, which shows antiferromagnetic coupling. The trilayers with Ru spacer layer thickness larger than 20 \AA exhibit only very weak ferromagnetic coupling.

1 - 23 of 23
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