Optimization of the Spin-Torque Oscillator Response for Microwave-Assisted Magnetic Recording

Microwave assisted magnetic recording (MAMR) is one of the promising next generation recording technologies that is expected to carry the magnetic recording industry beyond today's perpendicular magnetic recording (PMR) limit. MAMR involves the introduction of a high frequency oscillating magnetic field in the microwave frequency (GHz) range at the time of writing. This assisting energy at a specific frequency helps to make the magnetic grains more malleable and thereby reverse more easily which permits the usage of smaller, higher coercivity grains in the media, supporting a higher recording density. The generation of a stable oscillating magnetic field is expected to come from a spin-torque oscillator (STO) that has a rotating field-generating layer (FGL) when a current is injected. The STO must be properly designed in order to generate the stable oscillating magnetic field of the desired frequency and with sufficient amplitude to assist in the media reversal. In this work, we optimize the STO to produce a large and stable oscillating field with the desired parameters. Micromagnetic simulations of the STO are used to determine the STO's behavior and we propose various metrics to be used as a measure of the performance of the STO's response. Subsequently the response surface methodology (RSM) is employed to optimize our selected performance metric, producing the highest performing STO.