Fyzikální ústav Akademie věd ČR

Seminář Úterý, 09.06.2015 15:00 - 16:00

Přednášející: Kirill Belashchenko (University of Nebraska-Lincol)
Místo: UTIA, Pod vodárenskou věží č. 4, Praha 8, v seminární místnosti č. 25 v přizemí
Jazyk: anglicky
Pořadatelé: Oddělení teorie kondenzovaných látek

Abstract: Thermal spin fluctuations are present in equilibrium in all magnetic materials. These fluctuations interact with electronic quasiparticles and induce temperature-dependent changes in such observables as the spectral densities, magnetocrystalline anisotropy, and transport properties. This talk will review surprising examples of such effects in metallic magnets found using first-principles calculations. Spin fluctuations are included in these calculations within the vector disordered local moment model. First, effects of thermal spin disorder and excess Mn on the electronic spectrum of half-metallic NiMnSb will be discussed, suggesting that the Mn/Sb antisite defects may be the source of the observed low-temperature transport anomalies. Then, the electronic origin of the exotic concentration and temperature dependence of magnetocrystalline anisotropy in (Fe_1-xCo_x)2B alloys will be discussed, which is an unusual case of magnetic anisotropy increasing with decreasing magnetization - in stark contrast with conventional models. Finally, we will discuss a hidden resistivity saturation effect in gadolinium, which is attributed to the disorder-induced collapse of a large area of its Fermi surface.