Speakers: Ilja Turek (Department of Condensed Matter Physics, Faculty of Mathematics and Physics, Charles University, Prague)
Place: Na Slovance, main lecture hall
Presented in English
Organisers:
Division of Condensed Matter Physics
Abstract:
The seminar reviews the formulation and recent results of a fully
relativistic first-principles theory of metallic ferromagnetic systems.
The theory is based on the all- electron tight-binding linear muffin-tin
orbital (LMTO) method and the coherent potential approximation (CPA). Particular
attention will be devoted to the spin and orbital magnetic moments, total
energies, and transport properties.
As an example, the properties of random Fe-Co alloys in tetragonal
structures will be presented and discussed. These alloys were predicted to
exhibit a giant uniaxial magnetic anisotropy energy (MAE) which would make
them a promising material for magnetic recording. It will be shown that a
correct treatment of the chemical randomness present in real samples
reduces dramatically the MAE; the effect of a perfect and partial atomic
long-range order on the MAE will be briefly discussed as well.
In the last part, the anisotropy of static transport properties of these
alloys will be discussed with a focus on an orientation dependence of the
anomalous Hall conductivity (AHC). We have found that the AHC values for
the magnetization direction pointing along the tetragonal a and c axes can
differ nearly three times for certain tetragonal distortions and alloy
compositions. This anisotropy exceeds that calculated for the pure
tetragonal Fe and Co metals and it seems to be surprisingly stable with
respect to the alloy disorder.
(*) in collaboration with J. Kudrnovský, V. Drchal and K. Carva
Copyright © 2008-2014, Fyzikální ústav AV ČR, v. v. i.
