# Magnetodynamics in orthogonal nanocontact spin-torque nano-oscillators based on magnetic tunnel junctions

## TL;DR

This paper investigates the magnetodynamics of orthogonal magnetic tunnel junction-based spin-torque nano-oscillators, revealing high-frequency operation, tunability, and the dominant role of voltage-controlled magnetic anisotropy over spin transfer torque.

## Contribution

It provides a systematic analysis of microwave properties and physical origins in orthogonal MTJ STNOs, highlighting the significance of VCMA in frequency tunability.

## Key findings

- High emission frequencies above 20 GHz
- Frequency tunability of 0.25 GHz/mA
- Zero-field operation around 4 GHz

## Abstract

We demonstrate field and current controlled magnetodynamics in nanocontact spin-torque nano-oscillators (STNOs) based on orthogonal magnetic tunnel junctions (MTJs). We systematically analyze the microwave properties (frequency $f$, linewidth $\Delta f$, power $P$, and frequency tunability $df/dI$) with their physical origins---perpendicular magnetic anisotropy (PMA), damping-like and field-like spin transfer torque (STT), and voltage-controlled magnetic anisotropy (VCMA). These devices present several advantageous characteristics: high emission frequencies ($f> 20$ GHz), high frequency tunability ($df/dI=0.25$~GHz/mA), and zero-field operation ($f\sim 4$ GHz). Furthermore, a detailed investigation of $f(H, I)$ reveals that $df/dI$ is mostly governed by the large VCMA (287~fJ/(V$\cdot$m)), while STT plays a negligible role.