Frequency of Spin-Injection Radiation in the Magnetic Junction as a Function of the Spin Mobility of Electrons
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Frequency of Spin-Injection Radiation in the Magnetic Junction as a Function of the Spin Mobility of Electrons E. A. Vilkova, *, S. A. Nikitova, O. A. Byshevskii-Konopkoa, A. R. Safinb, L. A. Fominc, and S. G. Chigareva a Fryazino
Branch, Kotel’nikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Moscow, Russia b National Research University MEI, Moscow, Russia c Institute of Problems of Microelectronics Technology and High Purity Materials, Russian Academy of Sciences, Chernogolovka, Moscow oblast, Russia *e-mail: [email protected] Received March 26, 2020; revised March 26, 2020; accepted April 2, 2020
Abstract—Taking into account the difference in the mobilities of electrons with different spin projections, the frequencies of spin-injection radiation in the current-carrying magnetic contact formed by two ferromagnets are calculated. It is shown that these frequencies are in the terahertz range at a certain current density exceeding the threshold value, and the current density required to generate terahertz radiation can be, even at small values of the electron mobility difference, two orders of magnitude less than that in the absence of the electron mobility difference. The effect of the spin polarization ratio of ferromagnets that form a magnetic junction on the radiation frequency is analyzed. Keywords: magnetic transition, metallic ferromagnet, terahertz frequency, spin polarization DOI: 10.1134/S1063783420090322
1. INTRODUCTION Currently, magnetic nanocontacts with a spinpolarized current flowing through them are considered to be interesting objects to study [1–10]. This interest is determined by the prospects of their numerous applications in terahertz spintronics [11], threedimensional nanomagnetic devices [12], and memory devices and sensors [13]. It is known that spin injection through the nanocontact of two magnets by an electrical current can lead to substantial nonequilibrium spin accumulation in the region directly adjacent to the contact [3]. It has also been shown that the injection of hot electrons with nonequilibrium spins into the ferromagnet can give rise to the inverse population of its spin sub-bands [14]. In this case, the probability of radiative spin-flip transitions of conduction electrons can be significantly increased through the influence of the electromagnetic wave field on the s– d exchange interaction constant (exchange-enhanced transitions) [14, 15]. The radiation frequency of such transitions lies in the terahertz range, which is of interest from the perspective of creating terahertz lasers. However, there are many unsolved problems in the way toward creating lasers based on magnetic nanocontacts, for example, a necessity to overcome the high pumping current threshold. Nevertheless, the theoretically predicted threshold current values are
several orders of magnitude higher than the experimental ones observed during the detection of terahertz radiation [16, 17]. In our recent study [18], we have obtained an equation for nonequilibrium spin pol
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