Spin switching: From quantum to quasiclassical approach

Abstract

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.In this paper, we review the theory of spin switching for systems of different sizes, from a quantum mechanical master equation approach for small atomic clusters to the quasiclassical description of spin dynamics by a stochastic Landau-Lifshits-Gilbert equation in metallic nanoscale magnetic systems. We present characteristic results emphasizing the role of the quantum character of spin at different scales. Comparing the quantum mechanical and the quasiclassical approach to spin switching, we draw analogies between the factors affecting quantum and classical spin dynamics. We analyze assumptions used in each approach and emphasize the limits of applicability of the quantum mechanical and of the quasiclassical descriptions.

Magnetic moment of inertia within the torque-torque correlation model

“…For this purpose, “good” candidates are materials exhibiting thermally stable magnetic properties 3 , energy efficient magnetisation dynamics 4, 5 , as well as fast and stable magnetic switching 6, 7 . Various magnetic excitation methods 8–10 allow switching of the magnetic moment on sub-ps timescales.…”

“…The research on magnetic materials with particular focus on spintronics or magnonic applications became more and more intensified, over the last decades [1,2]. For this purpose, "good" candidates are materials exhibiting thermally stable magnetic properties [3], energy efficient magnetization dynamics [4,5], as well as fast and stable magnetic switching [6,7]. Especially the latter can be induced by i) an external magnetic field, ii) spin polarized currents [8], iii) laser induced all-optical switching [9], or iv) electric fields [10].…”

Symmetry effects on the spin switching of adatoms

“…While magnetic anisotropy introduces an energy cost for magnetization reversal, countless studies have illustrated that in the presence of strong magnetic anisotropy, individual magnetic adatoms still exhibit rather short lifetimes [6][7][8] owing to the interplay of the hybridization of the moment bearing orbitals and the underlying substrate. Such observations question the role of both tunneling electrons as well as substrate electrons in dynamical processes of the atomic spin [5,[9][10][11][12][13]. In order to enhance the dynamic stability of such adatoms, strong magnetic coupling between individual spins can be utilized to protect the total spin from fluctuations [2,14].…”

The geometric phase of Zn- and T-symmetric nanomagnets as a classification toolkit

“…In typical samples, the main mechanism for magnetization reversal are spin-flip events mediated by exchange interaction with substrate or tunneling electrons 36 43 44 45 46 47 , which can be described in its most general form, as…”