# Inducing out-of-plane precession of magnetization for microwave assisted magnetic recording using an oscillating polarizer in spin torque oscillator

## TL;DR

This paper demonstrates a novel spin torque oscillator design that induces out-of-plane precession of magnetization, enabling microwave assisted magnetic recording with a simple, thin structure and large cone angle oscillations.

## Contribution

The study introduces a new STO design using NiFe and FeCo layers, experimentally observing out-of-plane precession and its dynamics, supported by micromagnetic simulations.

## Key findings

- Observed out-of-plane precession mode oscillation in NiFe and FeCo layers.
- Achieved large cone angle of approximately 70 degrees for FeCo OPP mode.
- Demonstrated the potential for narrow gap magnetic recording head applications.

## Abstract

We investigated the dynamics of a novel design of spin torque oscillator (STO) for microwave assisted magnetic recording. Using Ni$_{80}$Fe$_{20}$ (NiFe) as the polarizer and Fe$_{67}$Co$_{33}$ (FeCo) as the field generating layer, we experimentally observed the magnetization reversal of NiFe, followed by multiple signals in the power spectra as the bias voltage increased. The signals reflected the out-of-plane precession (OPP) mode oscillation of both FeCo and NiFe, as well as the magnetoresistance effect of the STO device, which had the frequency equal to the difference between the oscillation frequency of NiFe and FeCo. Such dynamics were reproduced by micromagnetic simulation. In addition to the merit of realizing the OPP mode oscillation with a simple and thin structure suitable for a narrow gap recording head, the experimental results using this design suggested that a large cone angle of $\sim$ 70$^{\circ}$ for the OPP mode oscillation of FeCo was achieved, which was estimated based on the macrospin model.