Effect of Exchange Interaction Constants on the Magnetization Reversal in a Hard/Soft Magnetic Bilayer Model
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DISORDER, AND PHASE TRANSITION IN CONDENSED SYSTEM
Effect of Exchange Interaction Constants on the Magnetization Reversal in a Hard/Soft Magnetic Bilayer Model T. A. Taaeva,*, K. Sh. Khizrieva,b, and A. K. Murtazaeva,b a
Institute of Physics, Dagestan Scientific Center, Russian Academy of Sciences, Makhachkala, 367015 Russia b Dagestan State University, Makhachkala, 367000 Russia *e-mail: [email protected] Received January 16, 2019; revised March 16, 2019; accepted March 19, 2019
Abstract—A model is developed to study a hard/soft magnetic bilayer in an external magnetic field by the Monte Carlo method. The influence of the constants of the exchange intralayer and interlayer interactions of the hard magnetic and soft magnetic layers on the magnetization reversal in the magnetic bilayer is investigated. The formation of a spin spring is shown to be mainly determined by the exchange interaction in the soft magnetic layer. Phase diagrams are plotted for the magnetic bilayer. DOI: 10.1134/S1063776119070197
1. INTRODUCTION The magnetic multilayer structures consisting of alternating hard and soft magnetic layers are unique systems, which attract interest of researchers [1–15]. Kneller and Hawig [1] were the first to prepare hard/soft magnetic heterostructures, which were then called exchange-coupled or exchange-elastic magnets. Due to the exchange interaction between a soft magnetic layer (which has high saturation magnetization) and a hard magnetic layer (which has easy-axis anisotropy), these structures open up fresh opportunities for increasing energy product (BH)max [1, 3] and exhibit a number of unusual phenomena, such as the formation of a one-dimensional heterophase spin spring in an external magnetic field [2]. In addition, hard/soft magnetic heterostructures are promising for practical applications owing to the possibility of their incorporation into various electronic devices. The fabrication of ideal and proper magnetic heterostructures depends on many factors, such as the interface roughness and atomic mixing during growth. Structural defects can qualitatively change magnetic behavior and should be properly taken into account when experimental data are interpreted. All these difficulties in the fabrication and investigation of hard/soft magnetic heterostructures can be overcome using a numerical experiment and highly effective Monte Carlo methods [16]. For example, the temperature dependences of thermodynamic parameters and the critical behavior of a hard/soft magnetic bilayer were studied by Monte Carlo simulation [17, 18]. The temperature dependences of heat capacity and magnetic susceptibility had double maxima, which were caused by two phase transitions occurring
in the system [17]. Using finite-size scaling relations, we [18] calculated the static critical exponents of heat capacity α, magnetization β, susceptibility γ, and correlation radius ν, which agreed well with the theoretical predictions of the XY model. In [19], we studied the influence of a soft magnetic phase on the magnetization reversal in
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