Mechanism of parametric pumping of magnetization precession in a nanomagnet. Parametric mechanism of current-induced magnetization reversal

Abstract

A mechanism of current-induced magnetization reversal based on the parametric resonance is described. The source of the magnetization reversal is a current-induced magnetic field, which is applied perpendicularly to the easy axis of magnetic anisotropy of a ferromagnetic nanomagnet. The current-induced magnetic field was measured in a FeCoB nanomagnet to be 60 Gauss at a current density of 65 mA/um2. Two mechanisms of the magnetization reversal are described and calculated. The first mechanism is the reversal by a RF electrical current, which modulated at a frequency close to the precession frequency of the nanomagnet. The second mechanism is the reversal by a DC electrical current, in which the magneto-resistance and the current dependency of the induced magnetic field create a positive feedback loop, which amplifies a random tiny thermal fluctuation into a large magnetization precession leading to the magnetization reversal. The combination of the proposed mechanism with conventional magnetization-reversal mechanisms such as the Spin Torque and the Spin-Orbit Torque can improve the performance of a Magnetic Random Access Memory.