Publication Date:
2016-05-03
Description:
A study of how the total magnetization of a Ni-Fe heterostructure evolves during the relaxation of non-equilibrium, inhomogeneous, magnetization distributions toward an equilibrium state. These distributions occur within the framework of a superdiffusive mechanism of ultrafast demagnetization, after exposure to a femtosecond laser pulse. We account for relativistic (local) and exchange (non-local) relaxation mechanisms. This question is all the more interesting because exchange relaxation conserves the total magnetization of the sample. For sufficiently smooth distributions (typical dimensions are about several tens of nanometers), the evolution of the total magnetization is determined by different rates of relativistic relaxation in Ni and Fe. However, for sufficiently inhomogeneous magnetization distributions (with a scale of several nanometers, which is realized in the experiment), non-local relaxation is manifested by the fact that the spin current transfers magnetization from the Fe layer to Ni. As such, the difference in the rates of relativistic relaxation in Ni and Fe is expressed to a lesser extent. It is shown that for experimentally realized parameters of magnetic distribution in magnetic heterostructures, the variation of total magnetization decreases by more than two times, due to the spin current.
Print ISSN:
1063-777X
Electronic ISSN:
1090-6517
Topics:
Physics
