Room temperature skyrmions at zero field in exchange-biased ultrathin films

TL;DR

This paper reports the stabilization of room-temperature, zero-field magnetic skyrmions in exchange-biased multilayer films, demonstrating their potential for memory device applications through advanced magnetic imaging techniques.

Contribution

It introduces a method to stabilize skyrmions at room temperature and zero magnetic field in exchange-biased multilayers, advancing skyrmion-based memory technology.

Findings

Skyrmions with ~60 nm diameter stabilized at room temperature and zero field.

Exchange bias enhances skyrmion stability against moderate external magnetic fields.

Magnetic imaging confirms skyrmion presence and stability without external field.

Abstract

We demonstrate that magnetic skyrmions with a mean diameter around 60 nm can be stabilized at room temperature and zero external magnetic field in an exchange-biased Pt/Co/NiFe/IrMn multilayer stack. This is achieved through an advanced optimization of the multilayer stack composition in order to balance the different magnetic energies controlling the skyrmion size and stability. Magnetic imaging is performed both with magnetic force microscopy and scanning Nitrogen-Vacancy magnetometry, the latter providing unambiguous measurements at zero external magnetic field. In such samples, we show that exchange bias provides an immunity of the skyrmion spin texture to moderate external magnetic field, in the tens of mT range, which is an important feature for applications as memory devices. These results establish exchange-biased multilayer stacks as a promising platform towards the effective realization of memory and logic devices based on magnetic skyrmions.