# Investigation of the Dzyaloshinskii-Moriya interaction and room temperature skyrmions in W/CoFeB/MgO thin films and microwires

## TL;DR

This study quantifies the Dzyaloshinskii-Moriya interaction in W/CoFeB/MgO thin films and microwires, demonstrating room temperature skyrmion stabilization and the influence of composition and growth conditions on magnetic properties.

## Contribution

It introduces two measurement schemes to quantify DMI and shows how DMI and skyrmion stability depend on material composition and fabrication parameters.

## Key findings

- DMI values of approximately 0.7 mJ/m2 at the HM/FM interface.
- Room temperature stabilization of skyrmions in the studied films.
- Higher deposition rates improve film uniformity and skyrmion manipulability.

## Abstract

Recent studies have shown that material structures, which lack structural inversion symmetry and have high spin-orbit coupling can exhibit chiral magnetic textures and skyrmions which could be a key component for next generation storage devices. The Dzyaloshinskii-Moriya Interaction (DMI) that stabilizes skyrmions is an anti-symmetric exchange interaction favoring non-collinear orientation of neighboring spins. It has been shown that material systems with high DMI can lead to very efficient domain wall and skyrmion motion by spin-orbit torques. To engineer such devices, it is important to quantify the DMI for a given material system. Here we extract the DMI at the Heavy Metal (HM) /Ferromagnet (FM) interface using two complementary measurement schemes namely asymmetric domain wall motion and the magnetic stripe annihilation. By using the two different measurement schemes, we find for W(5 nm)/Co20Fe60B20(0.6 nm)/MgO(2 nm) the DMI to be 0.68 +/- 0.05 mJ/m2 and 0.73 +/- 0.5 mJ/m2, respectively. Furthermore, we show that this DMI stabilizes skyrmions at room temperature and that there is a strong dependence of the DMI on the relative composition of the CoFeB alloy. Finally we optimize the layers and the interfaces using different growth conditions and demonstrate that a higher deposition rate leads to a more uniform film with reduced pinning and skyrmions that can be manipulated by Spin-Orbit Torques.

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Source: https://tomesphere.com/paper/1706.05987