Spin-Dependent Electron Transport in MeRAM
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AGNETISM
Spin-Dependent Electron Transport in MeRAM N. Kh. Useinova, *, A. P. Chuklanovb, D. A. Bizyaevb, N. I. Nurgazizovb, and A. A. Bukharaevb a Institute
b
of Physics, Kazan Federal University, Kazan, 420008 Russia Zavoisky Physical-Technical Institute, FRC Kazan Scientific Center, Russian Academy of Sciences, Kazan, 420029 Russia * e-mail: [email protected] Received March 26, 2020; revised March 26, 2020; accepted April 2, 2020
Abstract—The paper presents theoretical model of a straintronics magnetoelectric random-access memory (MeRAM) storage cell with configurational anisotropy. The MeRAM cell consists of ferromagnetic layers with different orientations of the quasi-uniform magnetization, which is divided into identical magnetic tunnel junction’s ferromagnet|insulator|ferromagnet, in the form of a sandwich of planar layers. The modified theory for magnetic tunnel junction is used to calculate the spin-dependent current and tunnel magnetoresistance like functions of orientations magnetizations of layers. Keywords: straintronics, magnetic hetero-structure, magnetic tunnel junction, spin-dependent current, tunnel magnetoresistance DOI: 10.1134/S1063783420090310
1. INTRODUCTION A large number of experimental works as well as theoretical studies have been devoted to the problem of controlling the magnetization of nanoparticles by induced mechanical stresses; see, for example, resent reviews on “straintronics” [1–4]. One of the approaches to super-dense magnetic recording of information is based on re-magnetization of singledomain particles. The situation when the co-direction and opposite direction of magnetization along some axis of symmetry of the particle corresponds to two possible logical states is the optimal configuration for magnetic recording. In this case, the magnetic rerecording process is nothing but magnetization rotation by 180° angle. Usually, such rotation is performed by the external magnetic field of the recording head [5] or by the spin-transfer torque effect [6]. A relatively novel physical challenge is a realization of switching the magnetization direction of single-domain nanoparticles using an electric field through mechanical stress. This problem deserves fundamental consideration, since its solution would drastically reduce energy consumption and ensure high reliability of information recording and storage. Information carriers in single-domain magnetic nanoparticles are the spins of conduction electrons; the exchange interaction between them maintains their collective behavior during re-magnetization. Together, they behave like a quasi-classical system with a giant magnetic moment, which serves as an elementary information carrier [7, 8]. Moreover, a single-domain particle is less sensitive to noises at room temperature than a single-spin
device [9]. Therefore, recording the information on the base of single-domain anisotropic micro- or nanoparticles with, for example, two stable orientations of magnetization have certain advantages, viz. a very small dissipated energy for switching
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