Precession of Magnetization of a Spin-Valve Free Layer and Its Switching under the Effect of a Magnetic Field Perpendicular to the Anisotropy Axis

Abstract

Modern microelectronic devices based on layered spin-valve structures have low power inputs, a high reliability, and a broad temperature range. Studying dynamic spin-valve modes and the possibilities of controlling these modes are of practical interest. In this work, the operating modes of a spin valve, which comprise the base for magnetoresistive random-access memory (MRAM), a binary stochastic neuron (p-bit), and various spin-transfer nanooscillators (STNOs) are considered. A mathematical model of the spin valve with longitudinal anisotropy placed into a magnetic field parallel to the anisotropy axis and perpendicular to the plane of layers is constructed. A set of equations that describe the dynamics of the magnetization vector of the free layer of the spin valve is derived. Quantitative analysis of the set of equations enables determination of the equilibrium positions of magnetization of the free layer for the spin-valve structure. The conditions for changing the type of singular points of the dynamic set of equations are found based on the bifurcation analysis of the set. Investigation into the dynamics of the magnetization vector of the free layer of a spin valve enables determination of its main operational modes as the component of the magnetoresistive random access memory, binary stochastic neuron, and spin-transfer nanooscillator, as well as the ranges of the current and magnetic field corresponding to these modes. The frequency and amplitude characteristics are calculated for spin-valve oscillators. The proposed structure with anisotropy located in a field perpendicular to the anisotropy axis is more preferable when compared to a structure with a field applied parallel to the anisotropy axis from the viewpoint of its application as the spin-transfer nanooscillator.