Problems of spin and orbital dynamics connected with femtosecond optical switching
M.I. Kurkin and N.B. Orlova
Institute of Metal Physics , S. Kovalevskoyi st. 18, Ekaterinburg 620219, Russia
Received December 14, 2010
In this paper we analyze some peculiarities of the orbital and spin dynamics of ferromagnetics caused by
femtosecond laser pulses. We assume that during the femtosecond optical pump only orbital momenta of electrons have time to change. The spin switching occurs during a subnanosecond time typical for spin a dynamics after turning off the pump. The reason of the spin switching is the spin-orbital field of the orbital momenta created by the orbital pump. Suppression of quantum fluctuations of the orbital momenta is needed for the realization of the coherent condition of the nonequilibrium orbital momenta that is necessary for
the spin switching. These fluctuations are caused by the tunnel transitions between the degenerate states (by sign of the magnetic quantum number) of the orbital momenta in the crystal field. We analyze the possibility of such suppression by the means of the interatomic interaction of the orbital momenta analogous to the intra-atomic interorbital interaction connected with
the second Hund rule.
PACS: 75.40.Gb Dynamic properties; PACS: 75.60.Jk Magnetization reversal mechanisms; PACS: 42.65.Re Optical bistability, multistability, and switching, including local field effects.
Key words: femtomagnetism, spin dynamics, orbital magnetism, magnetooptics, quantum phase transition.