Nanoscale physics

On spintronics of multilayer magnetic nanostructures 
Korostil A.A1., Krupa M.M.1  

1Department of Physics of Meso- and Nanocrystalline Magnetic Structures, Institute of Magnetism NAS and MES  of Ukraine.  Vernadsky av., 36b, Kyiv, Ukraine. E-mail: amand@rambler.ru

The exchange interaction between the spin polarized states of conductivity electrons and localized spin states in multilayer magnetic structures underlies the effects of electric field-controlled change of localized magnetic stages and the spin dependent electron scattering which depends on the configuration of the localized magnetic states. The efficiency of the first effect characterizes by the threshold spin current density which is sufficient to overcome the magnetic anisotropy forces. In this context, the most favorable is the generation of spin current and spin polarization through the spin-orbit interaction when, in contrast to the generation through an effective magnetic field of an magnetic polarizer, the spin current is not accompanied by charge transfer and power consumption. 
For the ferromagnetic multilayer nanostructures, the mentioned two effects are associated with electric controlled magnetization dynamics and switching and also the magnetoresistance effect that are related to processes of magnetic writing and reading information. In the antiferromagnetic case (possessing zero magnetization) the mentioned spin interaction results in the controlled dynamics of antiferromagnetic order vector that is currently a completely unsolved problem. Thus, it is relevant the study of the electric field-controlled magnetization dynamics and the magnetoresistance effect in ferromagnetic nanostructures, in particular, in the tunnel ferromagnetic nanostructures.
The microscopic  description of  the  electric-controlled dynamics in the tunnel multilayer ferromagnetic nanostructures is based on the modified for magnetic system theory of non-equilibrium  Green functions with the real-time propagation of the embedded Kadanof-Baym equations which are quantum-kinetic equations for the one-particle propagator. It is shown, that these equation in the tight-binding representation systematically describe  features of the spin dependent tunneling and the spin torque effect with respect to localized magnetic moments.

This work was supported by the European project H2020-MSCA-RISE-2017-778308-SPINMULTIFILM.