Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 69: Superconductivity: Fe-based Superconductors - Theory
TT 69.10: Vortrag
Freitag, 15. März 2013, 12:00–12:15, H21
Theoretical study of magneto-crystalline anisotropy in Fe pnictides — •Alexander Yaresko — MPI FKF, Stuttgart, Germany
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. In this work it is shown 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, which correspond to reduced Fe moments, the order of the MCA energies is reverted: in agreement with the experiment the in-plane ab anisotropy becomes stronger. The microscopic origin of MCA in pnictides is also discussed.