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Growth and Magnetic Properties of Fe- and FeNi-based Thin Films and Multilayers
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the growth and magnetic properties of thin films and multilayers. The samples were grown by magnetron sputtering, and characterized structurally mainly by x-ray diffraction and reflectivity. The magnetic characterization of the multilayers was done by magneto-optical Kerr technique, SQUID magnetometry and, in two samples, by neutron reflectometry.

Arrays of small elements of polycrystalline permalloy (FeNi alloy with 19 wt% Fe) are of interest as a component in non-volatile magnetic random access memories (MRAM). Here the shape dependence of the domain structure in such elements was studied by magnetic force microscopy (MFM) and in thin ring magnets the 'onion' state could be seen for the first time. Also, by post-annealing in hydrogen atmosphere the number of domains decreased in each element due to enhanced relaxation and defect reduction.

Furthermore, permalloy-based anisotropic magnetoresistance (AMR) in read heads are nowadays replaced by material combinations that have a giant magnetoresistance (GMR) effect. In this work Fe/V(001) and Fe0.82Ni0.18/V(001) superlattices, i.e. single-crystal-like multilayers, were investigated. These systems showed much smaller GMR effect compared to the Fe/Cr system. However, by introducing Ni into the Fe layers the magnetic anisotropy and the interlayer exchange coupling (IEC) decreased, thereby increasing the sensitivity, which is a key property for a magnetic sensor. The interface region showed a reduced magnetic moment, and the influence of the structural quality was modelled and investigated theoretically in the Fe0.82Ni0.18/V case. Also, in the Fe(2-3 ML)/V(x ML) superlattices (ML=monolayers) the transition temperature from long-range magnetic order to paramagnetic order oscillated with the V layer thickness (x) as a result of the oscillatory behaviour of the IEC.

The introduction of hydrogen in the non-magnetic layers of, for example, Fe/V(001) superlattices is a way to tune the IEC strength. Here the tuning was used as a tool to study the magnetic order in a low-dimensional magnet. At the critical hydrogen concentration <H/V>=0.022 the Fe layers in an Fe(2 ML)/V(13 ML) superlattice became decoupled. Then the system behaved as a two-dimensional Ising magnet with a finite ordering temperature of about 60 K.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2004. , p. 62
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 927
Keywords [en]
Physics, Sputter growth, Permalloy, Multilayer, Superlattice, Magnetism
Keywords [sv]
Fysik
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-3940ISBN: 91-554-5849-1 (print)OAI: oai:DiVA.org:uu-3940DiVA, id: diva2:163933
Public defence
2004-02-13, Polhemssalen, Ångström laboratoriet, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 10:15
Opponent
Supervisors
Available from: 2004-01-19 Created: 2004-01-19Bibliographically approved
List of papers
1. Magnetic properties of submicron permalloy elements: Effects of heat treatment
Open this publication in new window or tab >>Magnetic properties of submicron permalloy elements: Effects of heat treatment
2003 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, no 10, p. 7334-7336Article in journal (Refereed) Published
Abstract [en]

We present the results of the effect of annealing in hydrogen atmosphere on the magnetic properties of continuous magnetic films and patterned structures. Rectangular and elliptical particles, with lateral dimensions in the range 150–900 nm, were made of 24 and 66 nm thick permalloy films. The domain structure and the magnetization reversal processes were investigated by magnetic force microscopy and alternating gradient magnetometry. While the performed annealing at 200 °C during 48 h did not noticeably change the properties of the continuous films, it influenced the patterned structures significantly. The difference between patterned elements and the continuous films can be explained by enhanced relaxation and vacancy diffusion in the particles

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-91254 (URN)10.1063/1.1543862 (DOI)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2017-12-14Bibliographically approved
2. Domain structure of circular and ring magnets
Open this publication in new window or tab >>Domain structure of circular and ring magnets
2003 (English)In: Journal of Magnetism and Magnetic Materials, Vol. 258-259, p. 348-351Article in journal (Refereed) Published
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-91255 (URN)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2012-03-07Bibliographically approved
3. Magnetic properties and coupling in Fe(2 ML)/V(x ML) (x>5) superlattices
Open this publication in new window or tab >>Magnetic properties and coupling in Fe(2 ML)/V(x ML) (x>5) superlattices
Show others...
2002 (English)In: Journal of Magnetism and Magnetic Materials, Vol. 246, p. 54-61. Erratum submitted 2003.Article in journal (Refereed) Published
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-91256 (URN)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2012-03-07Bibliographically approved
4. On the magnetic ordering in interleaved Fe(3 ML)/V(y ML)/Fe(2 ML)/V(y ML) superlattices
Open this publication in new window or tab >>On the magnetic ordering in interleaved Fe(3 ML)/V(y ML)/Fe(2 ML)/V(y ML) superlattices
2002 (English)In: Journal of Physics: Condensed Matter, Vol. 14, p. 12575-12583Article in journal (Refereed) Published
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-91257 (URN)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2012-01-27Bibliographically approved
5. Magnetic Superlattices with Variable Interlayer Exchange Coupling: A New Approach for the Investigation of Low-Dimensional Magnetism
Open this publication in new window or tab >>Magnetic Superlattices with Variable Interlayer Exchange Coupling: A New Approach for the Investigation of Low-Dimensional Magnetism
Show others...
2003 (English)In: Physical Review Letter, Vol. 91, no 3, p. 037202-1-4Article in journal (Refereed) Published
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-91258 (URN)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2012-01-27Bibliographically approved
6. Growth and characterization of Fe0.82Ni0.18/V(001) superlattices
Open this publication in new window or tab >>Growth and characterization of Fe0.82Ni0.18/V(001) superlattices
2003 (English)In: Journal of Physics: Condensed Matter, Vol. 15, p. 625-633Article in journal (Refereed) Published
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-91259 (URN)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2012-04-03Bibliographically approved
7. Influence of interface mixing on the magnetic properties of BCC Fe0.82Ni0.18/V (001) superlattices
Open this publication in new window or tab >>Influence of interface mixing on the magnetic properties of BCC Fe0.82Ni0.18/V (001) superlattices
Show others...
2003 In: Journal of Magnetism and Magnetic Materials, Vol. 267, p. 234-243Article in journal (Refereed) Published
Identifiers
urn:nbn:se:uu:diva-91260 (URN)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2013-03-21
8. Magnetic phase diagram of Fe0.82Ni0.18/V(001) superlattices
Open this publication in new window or tab >>Magnetic phase diagram of Fe0.82Ni0.18/V(001) superlattices
Show others...
(English)Manuscript (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-91261 (URN)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2013-03-21
9. Magnetic properties of an antiferromagnetically coupled bcc Fe0.82Ni0.18/V(001) superlattice
Open this publication in new window or tab >>Magnetic properties of an antiferromagnetically coupled bcc Fe0.82Ni0.18/V(001) superlattice
(English)Manuscript (Other academic)
National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-91262 (URN)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2012-01-27Bibliographically approved
10. Magnetic moments and exchange interactions in Fe0.82Ni0.18/V bcc(001) multilayers
Open this publication in new window or tab >>Magnetic moments and exchange interactions in Fe0.82Ni0.18/V bcc(001) multilayers
Show others...
2004 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, no 9, p. 094421-Article in journal (Refereed) Published
Abstract [en]

The magnetic ordering and average magnetization of multilayers are greatly affected by the interface structure of the system. In this paper, interface effects are discussed, and their impact on the amplitude and period of the interlayer exchange coupling and the magnetic moments are investigated for the Fe0.82Ni0.18∕V body-centered-cubic (001) system. By modeling these effects by first principles calculations we find good agreement with experiments over the whole investigated range of layer thicknesses. In addition, as different interface effects give different fingerprints on the interlayer exchange coupling and magnetization, we are able to make an estimate of the interface structure of the different experimental samples by comparing experiment to theory.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-91263 (URN)10.1103/PhysRevB.70.094421 (DOI)
Available from: 2004-01-19 Created: 2004-01-19 Last updated: 2017-12-14Bibliographically approved

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