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Magnetic ordering in a weakly coupled Fe/V(001) superlattice
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
2002 (English)In: Physical Review B, ISSN 0163-1829, Vol. 66, no 22, 220402(R)- p.Article in journal (Refereed) Published
Abstract [en]

A large shift of the ordering temperature is observed in an Fe3/V13(001) superlattice upon altering the interlayer coupling J′. The modification of J′ is accomplished by temporary alloying of the V spacer layers with hydrogen. A phase with short-range magnetic order is found in a wide temperature range between the paramagnetic phase and the onset of long-range order. It is interpreted as two-dimensional-XY behavior and is attributed to the absence of an in-plane magnetic anisotropy and the vanishing of the interlayer exchange coupling close to the ordering temperature.

Place, publisher, year, edition, pages
2002. Vol. 66, no 22, 220402(R)- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-93060DOI: 10.1103/PhysRevB.66.220402OAI: oai:DiVA.org:uu-93060DiVA: diva2:166424
Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-01-09
In thesis
1. Materials for Magnetic Recording Applications
Open this publication in new window or tab >>Materials for Magnetic Recording Applications
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In the first part of this work, the influence of hydrogen on the structural and magnetic properties of Fe/V(001) superlattices was studied. The local structure of the vanadium-hydride layers was determined by extended x-ray absorption fine structure (EXAFS) measurements. The magnetic ordering in a weakly coupled Fe/V(001) superlattice was investigated using the magneto-optical Kerr effect (MOKE). The interlayer exchange coupling is weakened upon alloying with hydrogen and a phase with short-range magnetic order was observed.

The second part is concerned with first-principles calculations of magnetic materials, with a focus on magnetic recording applications. The uniaxial magnetic anisotropy energy (MAE) of Fe, Co, and Ni was calculated for tetragonal and trigonal structures. Based on an analysis of the electronic states of tetragonal Fe and Co at the center of the Brillouin zone, tetragonal Fe-Co alloys were proposed as a material that combines a large uniaxial MAE with a large saturation magnetization. This was confirmed by experimental studies on (Fe,Co)/Pt superlattices. The large uniaxial MAE of L10 FePt is caused by the large spin-orbit interaction on the Pt sites in connection with a strong hybridization between Fe and Pt. Furthermore, it was shown that the uniaxial MAE can be increased by alloying the Fe sublattice with Mn. The combination of the high-moment rare-earth (RE) metals with the high-TC 3d transition metals in RE/Cr/Fe multilayers (RE = Gd, Tb, Dy) gives rise to a strong ferromagnetic effective exchange interaction between the Fe layers and the RE layer. The MAE of hcp Gd was found to have two principal contributions, namely the dipole interaction of the large localized 4f spins and the band electron magnetic anisotropy due to the spin-orbit interaction. The peculiar temperature dependence of the easy axis of magnetization was reproduced on a qualitative level.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. viii + 65 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 53
Keyword
Physics, magnetic materials, magnetic anisotropy, saturation magnetization, magnetic data storage, superlattice, hydrogen, density functional theory, first-principles calculations, two-dimensional magnetism, FP-LMTO, EXAFS, MOKE, Fysik
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-5800 (URN)91-554-6252-9 (ISBN)
Public defence
2005-05-20, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2011-05-05Bibliographically approved

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Hjörvarsson, Björgvin

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