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Magnus, Fridrik
Publications (10 of 24) Show all publications
Moubah, R., Magnus, F., Warnatz, T., Pálsson, G. K., Kapaklis, V., Ukleev, V., . . . Hjörvarsson, B. (2016). Discrete Layer-by-Layer Magnetic Switching in Fe/MgO(001) Superlattices. PHYSICAL REVIEW APPLIED, 5(4), Article ID 044011.
Open this publication in new window or tab >>Discrete Layer-by-Layer Magnetic Switching in Fe/MgO(001) Superlattices
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2016 (English)In: PHYSICAL REVIEW APPLIED, ISSN 2331-7019, Vol. 5, no 4, 044011Article in journal (Refereed) Published
Abstract [en]

We report on a discrete layer-by-layer magnetic switching in Fe/MgO superlattices driven by an antiferromagnetic interlayer exchange coupling. The strong interlayer coupling is mediated by tunneling through MgO layers with thicknesses up to at least 1.8 nm, and the coupling strength varies with MgO thickness. Furthermore, the competition between the interlayer coupling and magnetocrystalline anisotropy stabilizes both 90 degrees and 180 degrees periodic alignment of adjacent layers throughout the entire superlattice. The tunable layer-by-layer switching, coupled with the giant tunneling magnetoresistance of Fe/MgO/Fe junctions, is an appealing combination for three-dimensional spintronic memories and logic devices.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-297910 (URN)10.1103/PhysRevApplied.5.044011 (DOI)000374562100001 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2016-06-29 Created: 2016-06-28 Last updated: 2016-06-29Bibliographically approved
Magnus, F., Brooks-Bartlett, M. E., Moubah, R., Procter, R. A., Andersson, G., Hase, T. P., . . . Hjörvarsson, B. (2016). Long-range magnetic interactions and proximity effects in an amorphous exchange-spring magnet. Nature Communications, 7, Article ID 11931.
Open this publication in new window or tab >>Long-range magnetic interactions and proximity effects in an amorphous exchange-spring magnet
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2016 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, 11931Article in journal (Refereed) Published
Abstract [en]

Low-dimensional magnetic heterostructures are a key element of spintronics, where magnetic interactions between different materials often define the functionality of devices. Although some interlayer exchange coupling mechanisms are by now well established, the possibility of direct exchange coupling via proximity-induced magnetization through non-magnetic layers is typically ignored due to the presumed short range of such proximity effects. Here we show that magnetic order can be induced throughout a 40-nm-thick amorphous paramagnetic layer through proximity to ferromagnets, mediating both exchange-spring magnet behaviour and exchange bias. Furthermore, Monte Carlo simulations show that nearest-neighbour magnetic interactions fall short in describing the observed effects and long-range magnetic interactions are needed to capture the extent of the induced magnetization. The results highlight the importance of considering the range of interactions in low-dimensional heterostructures and how magnetic proximity effects can be used to obtain new functionality.

National Category
Other Physics Topics
Identifiers
urn:nbn:se:uu:diva-299738 (URN)10.1038/ncomms11931 (DOI)000378390000001 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationCarl Tryggers foundation The Swedish Foundation for International Cooperation in Research and Higher Education (STINT)
Available from: 2016-07-26 Created: 2016-07-26 Last updated: 2017-11-28Bibliographically approved
Dahlqvist, M., Ingason, A. S., Alling, B., Magnus, F., Thore, A., Petruhins, A., . . . Rosen, J. (2016). Magnetically driven anisotropic structural changes in the atomic laminate Mn2GaC. Physical Review B. Condensed Matter and Materials Physics, 93(1), Article ID 014410.
Open this publication in new window or tab >>Magnetically driven anisotropic structural changes in the atomic laminate Mn2GaC
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2016 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 93, no 1, 014410Article in journal (Refereed) Published
Abstract [en]

Inherently layered magnetic materials, such as magnetic M(n+1)AX(n) (MAX) phases, offer an intriguing perspective for use in spintronics applications and as ideal model systems for fundamental studies of complex magnetic phenomena. The MAX phase composition M(n+1)AX(n) consists of M(n+1)AX(n) blocks separated by atomically thin A-layers where M is a transition metal, A an A-group element, X refers to carbon and/or nitrogen, and n is typically 1, 2, or 3. Here, we show that the recently discovered magnetic Mn2GaC MAX phase displays structural changes linked to the magnetic anisotropy, and a rich magnetic phase diagram which can be manipulated through temperature and magnetic field. Using first-principles calculations and Monte Carlo simulations, an essentially one-dimensional (1D) interlayer plethora of two-dimensioanl (2D) Mn-C-Mn trilayers with robust intralayer ferromagnetic spin coupling was revealed. The complex transitions between them were observed to induce magnetically driven anisotropic structural changes. The magnetic behavior as well as structural changes dependent on the temperature and applied magnetic field are explained by the large number of low energy, i.e., close to degenerate, collinear and noncollinear spin configurations that become accessible to the system with a change in volume. These results indicate that the magnetic state can be directly controlled by an applied pressure or through the introduction of stress and show promise for the use of Mn2GaC MAX phases in future magnetoelectric and magnetocaloric applications.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-275544 (URN)10.1103/PhysRevB.93.014410 (DOI)000367779000005 ()
Funder
EU, FP7, Seventh Framework Programme, 258509Swedish Research Council, 642-2013-8020Swedish Research Council, 621-2011-4417Knut and Alice Wallenberg FoundationSwedish Research Council, 621-2011-4426
Available from: 2016-02-04 Created: 2016-02-04 Last updated: 2017-11-30Bibliographically approved
Frisk, A., Magnus, F., George, S., Arnalds, U. B. & Andersson, G. (2016). Tailoring anisotropy and domain structure in amorphous TbCo thin films through combinatorial methods. Journal of Physics D: Applied Physics, 49(3), Article ID 035005.
Open this publication in new window or tab >>Tailoring anisotropy and domain structure in amorphous TbCo thin films through combinatorial methods
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2016 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 49, no 3, 035005Article in journal (Refereed) Published
Abstract [en]

We apply an in-plane external magnetic field during growth of amorphous TbCo thin films and examine the effects on the magnetic anisotropy and domain structure. A combinatorial approach is employed throughout the deposition and analysis to study a continuous range of compositions between 7–95 at.% Tb. Magnetometry measurements show that all samples have a strong out-of-plane anisotropy, much larger than any in-plane components, regardless of the presence of a growth field. However, magnetic force microscopy demonstrates that the growth field does indeed have a large effect on the magnetic domain structure, resulting in elongated domains aligned along the imprinting field direction. The results show that the anisotropy can be tuned in intricate ways in amorphous TbCo films giving rise to unusual domain structures. Furthermore the results reveal that a combinatorial approach is highly effective for mapping out these material properties.

Keyword
magnetic anisotropy, amorphous magnetic materials, magnetic properties of thin films, domain structure
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-269248 (URN)10.1088/0022-3727/49/3/035005 (DOI)000368096300005 ()
Funder
Swedish Research CouncilThe Swedish Foundation for International Cooperation in Research and Higher Education (STINT)
Available from: 2015-12-18 Created: 2015-12-15 Last updated: 2017-12-01Bibliographically approved
Meshkian, R., Ingason, A. S., Arnalds, U. B., Magnus, F., Lu, J. & Rosen, J. (2015). A magnetic atomic laminate from thin film synthesis: (Mo0.5Mn0.5)(2)GaC. APL MATERIALS, 3(7), Article ID 076102.
Open this publication in new window or tab >>A magnetic atomic laminate from thin film synthesis: (Mo0.5Mn0.5)(2)GaC
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2015 (English)In: APL MATERIALS, ISSN 2166-532X, Vol. 3, no 7, 076102Article in journal (Refereed) Published
Abstract [en]

We present synthesis and characterization of a new magnetic atomic laminate: (Mo0.5Mn0.5)(2)GaC. High quality crystalline films were synthesized on MgO(111) substrates at a temperature of similar to 530 degrees C. The films display a magnetic response, evaluated by vibrating sample magnetometry, in a temperature range 3-300 K and in a field up to 5 T. The response ranges from ferromagnetic to paramagnetic with change in temperature, with an acquired 5T-moment and remanent moment at 3 K of 0.66 and 0.35 mu(B) per metal atom (Mo and Mn), respectively. The remanent moment and the coercive field (0.06 T) exceed all values reported to date for the family of magnetic laminates based on so called MAX phases.

National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-261307 (URN)10.1063/1.4926611 (DOI)000358923500003 ()
Funder
EU, FP7, Seventh Framework Programme, 258509Swedish Research Council, 642-2013-8020, 621-2012-4425
Available from: 2015-09-03 Created: 2015-09-01 Last updated: 2015-09-03Bibliographically approved
Procter, R. A., Magnus, F., Andersson, G., Sanchez-Hanke, C., Hjörvarsson, B. & Hase, T. P. (2015). Magnetic leverage effects in amorphous SmCo/CoAlZr heterostructures. Applied Physics Letters, 107(6), Article ID 062403.
Open this publication in new window or tab >>Magnetic leverage effects in amorphous SmCo/CoAlZr heterostructures
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2015 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 107, no 6, 062403Article in journal (Refereed) Published
Abstract [en]

Although magnetic heterostructures are the basis of many magnetic technologies, the mechanisms involved in magnetization reversals in such structures are not fully understood, especially in amorphous multilayers. Here, we report on the SmCo/CoAlZr system and exploit resonant magnetic x-ray scattering to probe the element specific magnetization reversals. When combined into a tri-layer structure, two different switching fields and reversal mechanisms are observed for the Sm and Co sub-lattices. We argue that the decoupling of the sub-lattices arises from the local distribution of atomic species within the amorphous matrix leading to a strong magnetic leverage effect and exchange pinning. The decoupling arises due to strong interactions between regions of high Co density which span the interface. The relatively sparse interactions between Sm and Co induce a localized pinning of the Co-rich areas, resulting in an exchange bias in minor loops and an enhanced coercivity.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-261960 (URN)10.1063/1.4928632 (DOI)000359794200017 ()
Funder
Swedish Research CouncilCarl Tryggers foundation Knut and Alice Wallenberg FoundationThe Swedish Foundation for International Cooperation in Research and Higher Education (STINT)
Available from: 2015-09-09 Created: 2015-09-07 Last updated: 2017-12-04
Petruhins, A., Ingason, A. S., Lu, J., Magnus, F., Olafsson, S. & Rosen, J. (2015). Synthesis and characterization of magnetic (Cr0.5Mn0.5)(2)GaC thin films. Journal of Materials Science, 50(13), 4495-4502.
Open this publication in new window or tab >>Synthesis and characterization of magnetic (Cr0.5Mn0.5)(2)GaC thin films
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2015 (English)In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 50, no 13, 4495-4502 p.Article in journal (Refereed) Published
Abstract [en]

Growth of (Cr0.5Mn0.5)(2)GaC thin films from C, Ga, and compound Cr0.5Mn0.5 targets is reported for depositions on MgO (111), 4H-SiC (0001), and Al2O3 (0001) with and without a NbN (111) seed layer. Structural quality is found to be highly dependent on the choice of substrate with MgO (111) giving the best results as confirmed by X-ray diffraction and transmission electron microscopy. Phase pure, high crystal quality MAX phase thin films are realized, with a Cr:Mn ratio of 1:1. Vibrating sample magnetometry shows a ferromagnetic component from 30 K up to 300 K, with a measured net magnetic moment of 0.67 mu(B) per metal (Cr + Mn) atom at 30 K and 5 T. The temperature dependence of the magnetic response suggests competing magnetic interactions with a resulting non-collinear magnetic ordering.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-255037 (URN)10.1007/s10853-015-8999-8 (DOI)000354093500005 ()
Funder
Swedish Research Council, 642-2013-8020 621-2012-4425
Available from: 2015-06-24 Created: 2015-06-12 Last updated: 2017-12-04Bibliographically approved
Meshkian, R., Ingason, A. S., Dahlqvist, M., Petruhins, A., Arnalds, U. B., Magnus, F., . . . Rosen, J. (2015). Theoretical stability, thin film synthesis and transport properties of the Mon+1GaCn MAX phase. Physica Status Solidi. Rapid Research Letters, 9(3), 197-201.
Open this publication in new window or tab >>Theoretical stability, thin film synthesis and transport properties of the Mon+1GaCn MAX phase
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2015 (English)In: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 9, no 3, 197-201 p.Article in journal (Refereed) Published
Abstract [en]

The phase stability of Mon +1GaCn has been investigated using ab-initio calculations. The results indicate stability for the Mo2GaC phase only, with a formation enthalpy of 0.4 meV per atom. Subsequent thin film synthesis of Mo2GaC was performed through magnetron sputtering from elemental targets onto Al2O3 [0001], 6H-SiC [0001] and MgO [111] substrates within the temperature range of 500 degrees C and 750 degrees C. High structural quality films were obtained for synthesis on MgO [111] substrates at 590 degrees C. Evaluation of transport properties showed a superconducting behavior with a critical temperature of approximately 7 K, reducing upon the application of an external magnetic field. The results point towards the first superconducting MAX phase in thin film form.

Keyword
superconducting MAX phases, Mo2GaC, ab-initio calculations, magnetron sputtering, thin films
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-252030 (URN)10.1002/pssr.201409543 (DOI)000351674600009 ()
Available from: 2015-04-30 Created: 2015-04-28 Last updated: 2017-12-04Bibliographically approved
Moubah, R., Magnus, F., Hjörvarsson, B. & Andersson, G. (2014). Antisymmetric magnetoresistance in SmCo5 amorphous films with imprinted in-plane magnetic anisotropy. Journal of Applied Physics, 115(5), 053911.
Open this publication in new window or tab >>Antisymmetric magnetoresistance in SmCo5 amorphous films with imprinted in-plane magnetic anisotropy
2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 5, 053911- p.Article in journal (Refereed) Published
Abstract [en]

We report on magnetoresistance measurements in SmCo5 amorphous films with a giant imprinted magnetic anisotropy. At low applied field parallel to the easy axis, the magnetoresistance exhibits a hysteretic, square, and antisymmetric shape. The antisymmetry in the magnetoresistance is a result of the non-uniform distribution of the magnetization direction over the sample in conjunction with the extraordinary Hall effect. Moreover, the combination of anisotropic magnetoresistance measurements and magnetic domain imaging demonstrates that the symmetry depends on the magnetization orientation with respect to the applied field.

National Category
Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-218264 (URN)10.1063/1.4864716 (DOI)000331645900058 ()
Funder
Carl Tryggers foundation Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2014-02-10 Created: 2014-02-10 Last updated: 2017-12-06Bibliographically approved
Magnus, F., Moubah, R., Arnalds, U. B., Kapaklis, V., Brunner, A., Schäfer, R., . . . Hjörvarsson, B. (2014). Giant magnetic domains in amorphous SmCo thin films. Physical Review B. Condensed Matter and Materials Physics, 89(22), 224420-1-224420-5.
Open this publication in new window or tab >>Giant magnetic domains in amorphous SmCo thin films
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2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 22, 224420-1-224420-5 p.Article in journal (Refereed) Published
Abstract [en]

The potential for tuning of magnetic properties and the exceptional uniformity are among the features that make amorphous magnetic materials attractive for technology. Here it is shown that the magnetization reversal in amorphous SmCo thin films takes place through the formation of giant magnetic domains, over a centimeter across. The domain structure is found to be dictated by the direction of the imprinted in-plane easy axis and the film boundaries. This is a consequence of the size of the anisotropy and the structural uniformity of the films, which also allows the movement of millimeter-long domain walls over distances of several millimeters. The results demonstrate the possibility of tailoring the magnetic domain structure in amorphous magnets over a wide range of length scales, up to centimeters. Moreover, they highlight an important consequence of the structural perfection of amorphous films.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-230519 (URN)10.1103/PhysRevB.89.224420 (DOI)000339049000010 ()
Available from: 2014-09-08 Created: 2014-08-26 Last updated: 2017-12-05Bibliographically approved
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