Regensburg 2013 – scientific programme
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MA: Fachverband Magnetismus
MA 43: Magnetization Dynamics II of 3
MA 43.10: Talk
Thursday, March 14, 2013, 17:15–17:30, H22
Statistical moment equations for stochastic spin dynamics in phase space: a uniaxial paramagnet subjected to a dc bias field of arbitrary orientation — •William Coffey1, Yuri Kalmykov2, and Sergey Titov3 — 1Department of Electronic and Electrical Engineering, Trinity College, Dublin 2, Ireland — 2LAMP, University of Perpignan Via Domitia, 52, Ave. Paul Alduy, 66860 Perpignan, France — 3Kotelnikov Institute of Radio Engineering and Electronics RAS, Vvedenskii Sq. 1, Fryazino, Moscow reg., 141190, Russian Federation
Spin dynamics in a dissipative environment are treated via the evolution (master) equation for spin orientations in the phase space in the weak spin-bath coupling and high temperature limits. The explicit solution is written for an arbitrary spin Hamiltonian as a finite series of spherical harmonics analogous to the (infinite) Fourier series representation of the classical case governed by the Fokker-Planck equation. Therefore, the expansion coefficients, i.e., the statistical averages of the spherical harmonics may be determined from a differential-recurrence relation yielding the stochastic spin dynamics for arbitrary spin number S. For large S the differential-recurrence relations reduce to those generated by the Fokker-Planck equation. Thus the spin dynamics may be treated in a manner transparently linking to the classical representations, providing quantum corrections to classical averages. The method is illustrated via the magnetization relaxation of a uniaxial paramagnet with a dc field applied at an arbitrary angle to the easy axis.