Functional Keldysh Theory of Spin Torques
| dc.creator | Duine, R. A. | |
| dc.creator | Nunez, A. S. | |
| dc.creator | Sinova, Jairo | |
| dc.creator | MacDonald, A. H. | |
| dc.date | 2007-03-15 | |
| dc.date | 2007-07-18 | |
| dc.date.accessioned | 2026-07-07T08:18:50Z | |
| dc.date.available | 2026-07-07T08:18:50Z | |
| dc.description | We present a microscopic treatment of current-induced torques and thermal fluctuations in itinerant ferromagnets based on a functional formulation of the Keldysh formalism. We find that the nonequilibrium magnetization dynamics is governed by a stochastic Landau-Lifschitz-Gilbert equation with spin transfer torques. We calculate the Gilbert damping parameter $α$ and the non-adiabatic spin transfer torque parameter $β$ for a model ferromagnet. We find that $β\neq α$, in agreement with the results obtained using imaginary-time methods of Kohno, Tatara and Shibata [J. Phys. Soc. Japan 75, 113706 (2006)]. We comment on the relationship between $s-d$ and isotropic-Stoner toy models of ferromagnetism and more realistic density-functional-theory models, and on the implications of these relationships for predictions of the $β/α$ ratio which plays a central role in domain wall motion. Only for a single-parabolic-band isotropic-Stoner model with an exchange splitting that is small compared to the Fermi energy does $β/α$ approach one. In addition, our microscopic formalism incorporates naturally the fluctuations needed in a nonzero-temperature description of the magnetization. We find that to first order in the applied electric field, the usual form of thermal fluctuations via a phenomenological stochastic magnetic field holds. | |
| dc.description | 14 pages, 3 figures | |
| dc.identifier | https://arxiv.org/abs/cond-mat/0703414 | |
| dc.identifier | http://arxiv.org/abs/cond-mat/0703414 | |
| dc.identifier | Phys. Rev. B 75, 214420 (2007) | |
| dc.identifier | doi:10.1103/PhysRevB.75.214420 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/134570 | |
| dc.subject | Mesoscale and Nanoscale Physics | |
| dc.title | Functional Keldysh Theory of Spin Torques | |
| dc.type | text |