Magnetization switching by current and microwaves

Abstract

We propose a theoretical model of magnetization switching in a ferromagnetic multilayer by both electric current and microwaves. The electric current gives a spin transfer torque on the magnetization, while the microwaves induce a precession of the magnetization around the initial state. Based on numerical simulation of the Landau-Lifshitz-Gilbert (LLG) equation, it is found that the switching current is significantly reduced compared with the switching caused solely by the spin transfer torque when the microwave frequency is in a certain range. We develop a theory of switching from the LLG equation averaged over a constant energy curve. It was found that the switching current should be classified into four regions, depending on the values of the microwave frequency. Based on the analysis, we derive an analytical formula of the optimized frequency minimizing the switching current, which is smaller than the ferromagnetic resonance frequency. We also derive an analytical formula of the minimized switching current. Both the optimized frequency and the minimized switching current decrease with increasing the amplitude of the microwave field. The results will be useful to achieve high thermal stability and low switching current in spin torque systems simultaneously.

18 pages, 13 figures, published

References in corpus (8)

• Resonant Spin-Transfer-Driven Switching of Magnetic Devices Assisted by Microwave Current Pulses
• Spin torque switching of an in-plane magnetized system in a thermally activated region
• Magnetization reversal condition for a nanomagnet within a rotating magnetic field
• Spin Torque Oscillators with Thermal Noise: A Constant Energy Orbit Approach
• Critical current of spin transfer torque-driven magnetization dynamics in magnetic multilayers
• Nonlinear analysis of magnetization dynamics excited by spin Hall effect
• Magnetization switching by microwaves synchronized in the vicinity of precession frequency
• Magnetization switching by microwaves initially rotating in opposite direction to precession

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• Spin-torque switching and control using chirped oscillating currents
• Hybrid micromagnetic and atomistic modeling of magnetization dynamics induced by engineered defects
• Transition state theory characterizes thin film macrospin dynamics driven by an oscillatory magnetic field: Inertial effects
• Current-Induced Instability of a Perpendicular Ferromagnet in Spin Hall Geometry
• Transition state dynamics of a driven magnetic free layer
• Surface-induced reduction of the switching field in nanomagnets