Injectional Equilibrium Spin Polarization in a Magnetic Transition, Taking into Account the Electron Spin Mobility
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ELECTRONICS
Injectional Equilibrium Spin Polarization in a Magnetic Transition, Taking into Account The Electron Spin Mobility E. A. Vilkova, *, S. A. Nikitova, O. A. Byshevsky-Konopkoa, A. R. Safinb, L. A. Fominc, and S. G. Chigareva aFryazino
Branch, Institute of Radio Engineering and Electrons, Russian Academy of Sciences, Fryazino, Moscow oblast, 141190 Russia b National Research University MEI, Moscow, 111250 Russia cInstitute of Problems of Microelectrons Technology and High-Purity Materials, Russian Academy of Sciences, Chernogolovka, Moscow oblast, 142432 Russia *e-mail: [email protected] Received October 29, 2019; revised October 29, 2019; accepted November 25, 2019
Abstract—Taking into account the electron spin mobility, the paper considers the numerical solution to the equation for nonequilibrium spin polarization at the boundary of a magnetic contact with a current formed by two ferromagnets. The frequencies of spin injection radiation are calculated. It is shown that at a certain current density exceeding the threshold value, these frequencies lie in the terahertz frequency range. It was found that for the same terahertz frequency range, even for small values of the difference in the mobility of electrons with spin up and down, the current density can be two orders of magnitude lower than the current density with the same mobility. DOI: 10.1134/S1064226920080136
INTRODUCTION At present, magnetic nanotransitions between two magnets with spin-polarized current flowing through them are an interesting object of research [1–11], related to the prospects of their applications in terahertz spintronics [12], in three-dimensional nanomagnetic devices [13], and in storage devices and sensors [14]. Spin current injection through the nanocontact of two magnets can lead to significant nonequilibrium spin accumulation in the region immediately near the contact. In particular, an inverse population of spin subbands of a ferromagnet can arise, into which hot electrons without spin equilibrium are injected. In this case, radiative spin-flip transitions of conduction electrons are possible, which are stimulated indirectly via s–d-exchange interaction with an electromagnetic wave [15, 16]. The radiation frequency at such transitions is determined by the energy of the effective exchange splitting of the spin subbands and lies in the terahertz range [15], which is very attractive for practical applications. More recently, we [15] obtained an equation for nonequilibrium spin polarization at the boundary of a magnetic contact with a current formed by two ferromagnets, and estimated the frequency of the spin-flip transition between nonequilibrium Fermi quasilevels with allowance for indirect electron transitions. It is shown that at a certain current density exceeding the
threshold value, this frequency lies in the terahertz frequency range. However, in this and other studies [17‒19], it was always assumed that the mobilities of electrons with opposite spin directions are equal, although it is known that in ferromagnets,
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