Methods of electron transport in ab initio theory of spin stiffness
Abstract
We present an ab initio theory of the spin-wave stiffness tensor for ordered and disordered itinerant ferromagnets with pair exchange interactions derived from a method of infinitesimal spin rotations. The resulting formula bears an explicit form of a linear-response coefficient which involves one-particle Green's functions and effective velocity operators encountered in a recent theory of electron transport. Application of this approach to ideal metal crystals yields more reliable values of the spin stiffness than traditional ill-convergent real-space lattice summations. The formalism can also be combined with the coherent potential approximation for an effective-medium treatment of random alloys, which leads naturally to an inclusion of disorder-induced vertex corrections to the spin stiffness. The calculated concentration dependence of the spin-wave stiffness of random fcc Ni-Fe alloys can be ascribed to a variation of the reciprocal value of alloy magnetization. Calculations for random iron-rich bcc Fe-Al alloys reveal that their spin-wave stiffness is strongly reduced owing to the atomic ordering; this effect takes place due to weakly coupled local magnetic moments of Fe atoms surrounded by a reduced number of Fe nearest neighbors.
Keywords
Cite
@article{arxiv.2001.06279,
title = {Methods of electron transport in ab initio theory of spin stiffness},
author = {Ilja Turek and Josef Kudrnovsky and Vaclav Drchal},
journal= {arXiv preprint arXiv:2001.06279},
year = {2020}
}
Comments
10 pages, 4 figures, 2 tables; text slightly extended; accepted in Phys. Rev. B