Shaped angular dependence of the spin transfer torque and microwave generation without magnetic field

TL;DR

This paper demonstrates that specially designed nanopillars with a non-standard angular dependence of spin transfer torque can generate microwave oscillations without external magnetic fields, advancing spintronics applications.

Contribution

It provides experimental evidence of field-free microwave generation using nanopillars with a wavy angular dependence of spin transfer torque, supported by theoretical modeling.

Findings

Observation of large-angle precessions without applied magnetic field

Confirmation of theoretical predictions of wavy torque angular dependence

Potential for field-free spin transfer oscillators

Abstract

The generation of oscillations in the microwave frequency range is one of the most important applications expected from spintronics devices exploiting the spin transfer phenomenon. We report transport and microwave power measurements on specially designed nanopillars for which a non-standard angular dependence of the spin transfer torque (wavy variation) is predicted by theoretical models. We observe a new kind of current-induced dynamics that is characterized by large angle precessions in the absence of any applied field, as this is also predicted by simulation with such a wavy angular dependence of the torque. This type of non-standard nanopillars can represent an interesting way for the implementation of spin transfer oscillators since they are able to generate microwave oscillations without applied magnetic field. We also emphasize the theoretical implications of our results on the angular dependence of the torque.