Unexpected behaviour of magneto-crystalline anisotropy in Fe-pnictides

Datum

28.01.2013

Zeit

14:30 - 15:30

Sprecher

Dr. Alexander Yaresko

Zugehörigkeit

Max-Planck-Institut f¨ur Festk¨orperforschung, Stuttgart

Sprache

en

Hauptthema

Materialien

Andere Themen

Materialien, Physik

Host

Grit Rötzer

Beschreibung

If spin-orbit coupling is taken into account, LSDA band structure calculations for parent Fe pnictides successfully reproduce the correct magnetic ground state with stripe antiferromagnetic (AFM) order and Fe moments aligned along a, i.e., along AFM Fe chains. They also predict that the out-of-plane (ac) magneto-crystalline anisotropy (MCA) in LaFeAsO and BaFe2As2 is stronger than the in-plane (ab) one. However, recent polarized inelastic neutron scattering experiment showed the opposite: the gap at zone center is larger for in-plane spin excitations than for out-of-plane ones, which means that it is easier to deviate Fe spins in the ac plane. We show that MCA in LaFeAsO, BaFe2As2, and NaFeAs is a non-monotonous function of the exchange splitting of Fe d states. For large values of the splitting the out-of-plane MCA is stronger. However, for sufficiently small exchange splittings the order of the MCA energies is reverted: in agreement with the experiment the in-plane ab anisotropy becomes stronger. .

Links

• Seminars at the IFW

Letztmalig verändert: 28.01.2013, 08:56:54