Spin-transfer switching and low-field precession in exchange-biased spin valve nano-pillars

TL;DR

This paper reports the fabrication of nanopillar devices demonstrating spin transfer torque switching at zero magnetic field and low-field spin wave excitations influenced by exchange bias and spin-scattering asymmetry.

Contribution

It introduces a novel fabrication process for nanopillars showing zero-field spin transfer switching and analyzes the role of exchange bias in low-field spin wave excitations.

Findings

Spin transfer torque switching occurs at zero external magnetic field.

A field-dependent resistance peak indicates low-field spin wave excitation.

Exchange bias enhances spin-scattering asymmetry leading to observed phenomena.

Abstract

Using a three-dimensional focused-ion beam lithography process we have fabricated nanopillar devices which show spin transfer torque switching at zero external magnetic fields. Under a small in-plane external bias field, a field-dependent peak in the differential resistance versus current is observed similar to that reported in asymmetrical nanopillar devices. This is interpreted as evidence for the low-field excitation of spin waves which in our case is attributed to a spin-scattering asymmetry enhanced by the IrMn exchange bias layer coupled to a relatively thin CoFe fixed layer.