Ultrafast magnetization dynamics rates within the Landau-Lifshitz-Bloch model

Article

关键词: FEMTOSECOND LASER-PULSES;    CURIE-TEMPERATURE;    SPIN DYNAMICS;    METALS;    NICKEL;    ELECTRON;    FILMS;    RELAXATION;    RESONANCE;    DEMAGNETIZATION;   

DOI  :  10.1103/PhysRevB.84.144414

来源: SCIE

【 摘 要 】

Ultrafast laser-induced magnetization dynamics is analyzed in terms of the Landau-Lifshitz-Bloch (LLB) equation for different values of spin S. Within the LLB model the ultrafast demagnetization time (tau(M)) and the transverse damping (alpha(perpendicular to)) are parametrized by the intrinsic coupling-to-the-bath parameter lambda, defined by the microscopic spin-flip rate. We show that the LLB model is equivalent to a recently introduced M3TM model [B. Koopmans et al., Nature Mat. 9, 259 (2010)] with S = 1/2 within the assumption that the intrinsic scattering mechanism is the phonon-mediated Elliott-Yafet scattering. As a result, for this process lambda is proportional to the ratio between the nonequilibrium phonon and electron temperatures, in contrast to previous models with lambda = const. We investigate the influence of the finite spin number and the scattering rate parameter lambda on the ultrafast magnetization dynamics. The differences in the demagnetization time scale in transition metals and Gd are attributed to the fact that this parameter is almost two orders of magnitude smaller in the latter case. The relation between the femtosecond demagnetization rate and the perpendicular picosecond-nanosecond damping, provided by the LLB theory, is checked based on the available experimental data. A good agreement is obtained for Ni, Co, and Gd, providing validation of the LLB model.

【 授权许可】

Free