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Magnetic anisotropy of L10 FePt and Fe1-xMnxPt
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2005 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 71, no 13, 134411- p.Article in journal (Refereed) Published
Abstract [en]

The uniaxial magnetic anisotropy energy (MAE) of L10 FePt and Fe1−xMnxPt, x=0−0.25, was studied from first principles using two fully relativistic computational methods, the full-potential linear muffin-tin orbitals method and the exact muffin-tin orbitals method. It was found that the large MAE of 2.8 meV/f.u. is caused by a delicate interaction between the Fe and Pt atoms, where the large spin-orbit coupling of the Pt site and the hybridization between Fe 3d and Pt 5d states is crucial. The effect of random order on the MAE was modeled by mutual alloying of the sublattices within the coherent potential approximation (CPA), and a strong dependence of the MAE on the degree of chemical long-range order was found. The alloying of FePt with Mn was investigated with the virtual crystal approximation and the CPA as well as supercell calculations. The MAE increases up to 33% within the concentration range studied here, an effect that is attributed to band filling. Furthermore, the dependence of the MAE on the structural properties was studied.

Place, publisher, year, edition, pages
2005. Vol. 71, no 13, 134411- p.
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-93064DOI: 10.1103/PhysRevB.71.134411OAI: oai:DiVA.org:uu-93064DiVA: diva2:166428
Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2017-12-14Bibliographically approved
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
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Supervisors
Available from: 2005-04-28 Created: 2005-04-28 Last updated: 2011-05-05Bibliographically approved

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Burkert, TillEriksson, OlleSanyal, BiplabNordström, Lars

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