High-density N\xe9el-type magnetic skyrmion phase stabilized at high temperature

Hee Young Kwon,Seung-Young Park,Juyoung Jeong,Jun Woo Choi,Hye Jung Chang,Ah-Yeon Lee,Kyung Mee Song,Changyeon Won,Byoung-Chul Min,Jeehoon Kim

doi:10.1038/s41427-020-00270-z

Abstract

The discovery of a thermally stable, high-density magnetic skyrmion phase is a key prerequisite for realizing practical skyrmionic memory devices. In contrast to the typical low-density Néel-type skyrmions observed in technologically viable multilayer systems, with Lorentz transmission electron microscopy, we report the discovery of a high-density homochiral Néel-type skyrmion phase in magnetic multilayer structures that is stable at high temperatures up to 733 K (≈460 °C). Micromagnetic simulations reveal that a high-density skyrmion phase can be stabilized at high temperature by deliberately tuning the magnetic anisotropy, magnetic field, and temperature. The existence of the high-density skyrmion phase in a magnetic multilayer system raises the possibility of incorporating chiral Néel-type skyrmions in ultrahigh-density spin memory devices. Moreover, the existence of this phase at high temperature shows its thermal stability, demonstrating the potential for skyrmion devices operating in thermally challenging modern electronic chips.

Highlights

Skyrmions in magnetic materials have been extensively studied due to their nontrivial topology; this topology leads to many interesting fundamental and dynamical properties[1,2,3]
Correspondence: Hye Jung Chang or Jun Woo Choi 1Center for Spintronics, Korea Institute of Science and Technology, Seoul 02792, Republic of Korea 2Department of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of Korea Full list of author information is available at the end of the article These authors contributed : Hee Young Kwon, Kyung Mee Song, Juyoung Jeong temperature[10,11,12,13,14,15] and (2) they exhibit current driven unidirectional translation motion[12,16,17,18]. This motion is due to the electric current induced spin-orbit torque (SOT) acting on the homochiral Néel domain walls of the magnetic multilayer skyrmions; the SOT exerts a unidirectional force on the homochiral Néel domain walls, causing the skyrmions to move with or against the electric current direction depending on the chirality of the system[19]
In this study, using Lorentz transmission electron microscopy (LTEM), we discover a high-density homochiral Néeltype skyrmion phase in a magnetic multilayer system that is stable in a wide temperature range, even at high temperatures above 700 K

Summary

Introduction

Skyrmions in magnetic materials have been extensively studied due to their nontrivial topology; this topology leads to many interesting fundamental and dynamical properties[1,2,3]. Micromagnetic simulations confirm the experimental observations, showing that a high-density Néeltype skyrmion phase can be stabilized by appropriately tuning the temperature-dependent material parameters (e.g., magnetic anisotropy and magnetization).

Results

Conclusion