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Andersson, GabriellaORCID iD iconorcid.org/0000-0002-9479-1952
Publications (10 of 64) Show all publications
Frisk, A., Ahlberg, M., Muscas, G., George, S., Johansson, R., Klysubun, W., . . . Andersson, G. (2019). Magnetic and structural characterization of CoFeZr thin films grown by combinatorial sputtering. Physical Review Materials, 3(7), Article ID 074403.
Open this publication in new window or tab >>Magnetic and structural characterization of CoFeZr thin films grown by combinatorial sputtering
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2019 (English)In: Physical Review Materials, E-ISSN 2475-9953, Vol. 3, no 7, article id 074403Article in journal (Refereed) Published
Abstract [en]

We report on a detailed investigation of structural and magnetic properties of thin CoFeZr films, produced by combinatorial cosputtering, with compositions in the ranges 30–85 at.% Co, 12–63 at.% Fe, and 4–8 at.% Zr. Extended x-ray absorption fine structure and x-ray diffraction measurements reveal that alloys with a Zr content below 5 at.% are polycrystalline with a bcc structure, while an amorphous morphology is stabilized at Zr contents above 6 at.%. All samples display a growth-induced in-plane uniaxial anisotropy, which is closely related to the Zr concentration gradients across the wafers. A model for the angular dependence of the reduced remanence, including a Gaussian distribution of easy/hard anisotropy axes, is presented and successfully used to fit the data for all samples. The magnetic moments of the polycrystalline films approximately follow the Slater-Pauling curve, and the magnetic moments of the amorphous films follow a similar trend, but with about 20 % lower values. X-ray magnetic circular dichroism measurements show, for the amorphous films, that the Co moments are virtually constant at 1.7(2)μB/atom.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-305520 (URN)10.1103/PhysRevMaterials.3.074403 (DOI)000474390900005 ()
Funder
Swedish Research Council, C0514401Swedish Foundation for Strategic Research , RIF-14-0053
Available from: 2016-10-22 Created: 2016-10-18 Last updated: 2019-08-21Bibliographically approved
Frisk, A., Ali, H., Svedlindh, P., Leifer, K., Andersson, G. & Nyberg, T. (2018). Composition, structure and magnetic properties of ultra-thin Fe/Ni multilayers sputter deposited on epitaxial Cu/Si(001). Thin Solid Films, 646, 117-125
Open this publication in new window or tab >>Composition, structure and magnetic properties of ultra-thin Fe/Ni multilayers sputter deposited on epitaxial Cu/Si(001)
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2018 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 646, p. 117-125Article in journal (Refereed) Published
Abstract [en]

Sputter deposited symmetric multilayers of (n Fe)/(n Ni), with individual thicknesses from n = 4 to n = 48 monolayers (ML), were deposited on epitaxial Cu/Si(001), and their microstructural evolution and magnetic properties versus n have been studied. Elemental layering can be seen with transmission electron microscopy down to n = 4 ML layer thickness, although an intermixed region characterized by a finite interface width is found to be present. This width is composed of the interface roughness as well as the interdiffusion between layers, but the relative contributions from these two sources could not be concluded by the techniques used. The measured elemental layering and X-ray reflectivity (XRR) give an upper limit to the interface width which must be smaller than the thinnest layers, 4 ML. Electron energy loss spectroscopy (EELS), depth profiling X-ray photoelectron spectroscopy (XPS) and also XRR reveal that Fe has a higher tendency to mix with Ni than vice versa. XPS does not have the resolution to measure this thin elemental layering: composition variations for n = 8 ML which are clearly seen by EELS are barely resolved by XPS. The structure was determined by X-ray diffraction, and an epitaxial fcc (001) structure is found to be maintained throughout the multilayers up to n less than or similar to 8 ML. For larger n values, relaxation starts by Fe-fcc(001) layers changing into Fe-bcc(110), which is then followed by Ni-fcc(001) changing from (001) to (111) orientation along the growth direction. A decreased total measured magnetic moment for the fully epitaxial multilayers can be explained by the fcc Fe layers being partly anti-ferromagnetic, whereas the relaxed multilayers exhibit the expected magnetic properties of (bcc Fe) +(fcc Ni).

National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-305519 (URN)10.1016/j.tsf.2017.11.023 (DOI)000418575900017 ()
Funder
Swedish Research Council
Available from: 2016-10-22 Created: 2016-10-18 Last updated: 2019-12-06Bibliographically approved
Akansel, S., Venugopal, V., Kumar, A., Gupta, R., Brucas, R., George, S., . . . Svedlindh, P. (2018). Effect of seed layers on dynamic and static magnetic properties of Fe65Co35 thin films. Journal of Physics D: Applied Physics, 51(30), Article ID 305001.
Open this publication in new window or tab >>Effect of seed layers on dynamic and static magnetic properties of Fe65Co35 thin films
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2018 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 51, no 30, article id 305001Article in journal (Refereed) Published
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.

Keywords
Magnetization dynamics, magnetic thin films, Gilbert damping, ferromagnetic resonance
National Category
Condensed Matter Physics Engineering and Technology
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-345853 (URN)10.1088/1361-6463/aaccc0 (DOI)000437408700001 ()
Funder
Knut and Alice Wallenberg Foundation, 2012.0031
Available from: 2018-03-12 Created: 2018-03-12 Last updated: 2018-10-12Bibliographically approved
Frisk, A., Hase, T. P. .., Svedlindh, P., Johansson, E. & Andersson, G. (2017). Strain Engineering for Controlled Growth of Thin-Film FeNi L10. Journal of Physics D: Applied Physics, 50(8), Article ID 085009.
Open this publication in new window or tab >>Strain Engineering for Controlled Growth of Thin-Film FeNi L10
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2017 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 50, no 8, article id 085009Article in journal (Refereed) Published
Abstract [en]

FeNi thin films in the L1(0) phase were successfully grown by magnetron sputtering on HF-etched Si(001) substrates on Cu/Cu100-xNix buffers. The strain of the FeNi layer, (c/a)(FeNi), was varied in a controlled manner by changing the Ni content of the Cu100-xNix buffer layer from x = 0 at.% to x = 90 at.%, which influenced the common in- plane lattice parameter of the CuNi and FeNi layers. The presence of the L1(0) phase was confirmed by resonant x-ray diffraction measurements at various positions in reciprocal space. The uniaxial magnetocrystalline anisotropy energy K-U is observed to be smaller (around 0.35 MJ m(-3)) than predicted for a perfect FeNi L1(0) sample, but it is larger than for previously studied films. No notable variation in K-U with strain state (c/a)(FeNi) is observed in the range achieved (0.99 less than or similar to (c/a)(FeNi) less than or similar to 1.02), which is in agreement with theoretical predictions.

Keywords
x-ray diffraction, magnetic anisotropy, magnetic properties of monolayers and thin films, L1(0)
National Category
Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-305521 (URN)10.1088/1361-6463/aa5629 (DOI)000395674700006 ()
Funder
Swedish Research Council
Available from: 2016-10-22 Created: 2016-10-18 Last updated: 2017-05-08Bibliographically 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, article id 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
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, article id 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.

Keywords
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
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, article id 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
Zamani, A., Moubah, R., Ahlberg, M., Stopfel, H., Arnalds, U., Hallén, A., . . . Jönsson, P. (2015). Magnetic properties of amorphous Fe93Zr7 films: Effect of light ion implantation. Journal of Applied Physics, 117(14), Article ID 143903.
Open this publication in new window or tab >>Magnetic properties of amorphous Fe93Zr7 films: Effect of light ion implantation
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2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 14, article id 143903Article in journal (Refereed) Published
Abstract [en]

The Curie temperature (T-c) of amorphous FeZr alloys can be greatly enhanced by doping with light elements. In this investigation, ion implantation is used to dope Fe93Zr7 thin films with H, He, B, C, and N. Extended X-ray absorption fine structure measurements confirm that the amorphous structure is preserved upon implantation for all samples, except for the N-implanted sample which is partially crystallized. The Curie temperature increases from 124 K for the pristine FeZr sample to about 400 K for the (FeZr)B-0.11 sample. The increase of T-c is proportional to the increase in the average Fe-Fe distance, which allows us to conclude that the dominant cause of the T-c enhancement of amorphous Fe93Zr7 upon doping is a volume effect.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-252143 (URN)10.1063/1.4917212 (DOI)000352967400008 ()
Funder
Swedish Research Council
Available from: 2015-05-03 Created: 2015-05-03 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, p. 053911-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
Andersson Chronholm, J., Larsson, J. & Andersson, G. (2014). Förstaårsstudenters och lärares förhållningssätt till laborationer i fysik. In: : . Paper presented at NU 2014.
Open this publication in new window or tab >>Förstaårsstudenters och lärares förhållningssätt till laborationer i fysik
2014 (Swedish)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [sv]

Laborationer används som ett närmast självklart inslag på naturvetenskapliga utbildningar. Mål och syften med laborationer kan skifta mellan olika kurser och är inte alltid uppenbara för studenterna (Hart et al., 2000; Russell & Weaver, 2008). Ofta förväntas de lära sig hantering av utrustning, tolkning av data och rapportskrivning, samtidigt som de ska få bättre förståelse för teorin genom att se

Johan Larsson undersökte 2012 hur hans studenter på tekniskt-naturvetenskapligt basår (högskoleförberedande) värderade olika undervisningsformer. Laborationer fick då sämst betyg. För att undersöka möjliga orsaker till detta tog vi initiativ till en fenomenografisk studie (Marton, 1981) av attityder till fysiklaborationer. Skriftliga enkätsvar samlades in från 38 förstaårsstudenter på kandidatprogrammet i fysik vid Uppsala universitet. Den öppna enkätfrågan inspirerades av en amerikansk studie

besvarades även av 18 anonyma lärare på Institutionen för fysik och astronomi. Både lärare och studenter har skrivit långa svar som vi kategoriserat fenomenografiskt, det vill säga vi har kartlagt förekomsten av attityder.

Det finns tydliga nivåer av progression; från ett distanserat, ointresserat förhållningssätt till en nivå där man har en uppfattning om framtida behov. Studien visar inte på några större skillnader mellan lärarnas och studenternas syn. Laborationer förväntas koppla teori till praktik samt ge tillfälle att träna på instrumenthantering och vetenskapligt arbetssätt. Några nämner också att laborationer ökar deras förståelse och lärande, ger social träning och förbereder dem för ett kommande arbetsliv.

Vår avsikt är att använda resultaten för att öka laborationernas upplevda värde, genom att uppmärksamma kollegor på de förekommande förhållningssätten och tillsammans förbereda oss för att bemöta dem. Frågor som vi vill diskutera är t.ex.: Vill vi att studenterna ska tycka så här?

Hur speglar våra laborationsinstruktioner det vi vill att studenterna ska lära sig? Hur kommunicerar vi mål och syften med varje laboration på bästa sätt?

Hart C., Mulhall, P., Berry, A., Loughran, J., & Gunstone, R. (2000). What is the purpose of this experiment? Or can students learn something from doing experiments? Journal of Research in Science Teaching, 37(7), 655-675. Marton, F. (1981). Phenomenography Describing conceptions of the world around us. Instructional Science, 10, 177-200.

Russell, C. B., & Weaver, G. C. (2008). Student Perceptions of the Purpose and Function of the Laboratory in Science: A Grounded Theory Study. International Journal for the Scholarship of Teaching and Learning, 2(2), 1-14.

Keywords
laborationer
National Category
Other Physics Topics
Research subject
Physics with specialization in Physics Education
Identifiers
urn:nbn:se:uu:diva-262505 (URN)
Conference
NU 2014
Available from: 2015-09-15 Created: 2015-09-15 Last updated: 2015-09-15
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9479-1952

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