L. Udvardi, L. Szunyogh, K. Palotás, P. Weinberger:

"First-principles relativistic study of spin waves in thin magnetic films";

Physical Review B,68(2003), 104436/1 - 104436/11.

In order to study spin-wave excitations of itinerant ferromagnets a relativistic first-principles method based

on the adiabatic approach is presented. The derivatives of the free energy up to second order with respect of the

polar and azimuthal angles are derived within the framework of the magnetic force theorem and the fully

relativistic Korringa-Kohn-Rostoker method. Exchange and spin-orbit coupling are thus incorporated on equal

footing in the Hamiltonian. Furthermore, a detailed comparison to classical spin Hamiltonians is given and it

is shown that the magnetocrystalline anisotropy energy contains contributions from both the on-site anisotropy

and the off-site exchange coupling terms. The method is applied to an Fe monolayer on Cu~001! and Au~001!

surfaces and for a Co monolayer on Cu~001!. The calculations provide with the gap at zero wave number due

to the spin-orbit coupling and uniaxial anisotropy energies in good agreement with the results of the band

energy difference method. It is pointed out that the terms in the spin-wave Hamiltonian related to the mixed

partial derivatives of the free energy, absent within a nonrelativistic description, introduce an asymmetry in the

magnon spectrum with respect to two in-plane easy axes. Moreover, in the case of an in-plane magnetized

system the long-wavelength magnons are elliptically polarized due to the difference of the second-order

uniaxial and fourth-order in-plane magnetic anisotropy.

DOI: 10.1103/PhysRevB.68.104436 PACS number~s!: 75.10.Jm, 75.30.Ds, 75.30.Gw, 75.70.Ak

http://aleph.ub.tuwien.ac.at/F?base=tuw01&func=find-c&ccl_term=AC04405807

http://www.cms.tuwien.ac.at/publications/pdf2003/PRB68-104436-03.pdf

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