High-density, spontaneous magnetic biskyrmions induced by negative thermal expansion in ferrimagnets

Yuzhu Song; Tiankuo Xu; Guoping Zhao; Yuanji Xu; Zhicheng Zhong; Xinqi Zheng; Naike Shi; Chang Zhou; Yiqing Hao; Qingzhen Huang; Xianran Xing; Ying Zhang; Jun Chen

doi:10.1126/sciadv.adi1984

High-density, spontaneous magnetic biskyrmions induced by negative thermal expansion in ferrimagnets

Sci Adv. 2023 Sep 8;9(36):eadi1984. doi: 10.1126/sciadv.adi1984. Epub 2023 Sep 6.

Authors

Yuzhu Song¹, Tiankuo Xu², Guoping Zhao³, Yuanji Xu⁴, Zhicheng Zhong⁵, Xinqi Zheng⁶, Naike Shi¹, Chang Zhou⁷, Yiqing Hao⁸, Qingzhen Huang⁹, Xianran Xing¹⁰, Ying Zhang², Jun Chen¹

Affiliations

¹ Beijing Advanced Innovation Center for Materials Genome Engineering, Department of Physical Chemistry, University of Science and Technology Beijing, Beijing 100083, China.
² Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
³ College of Physics and Electronic Engineering and Institute of Solid State Physics, Sichuan Normal University, Chengdu 610066, China.
⁴ Institute for Applied Physics, University of Science and Technology Beijing, Beijing 100083, China.
⁵ Key Laboratory of Magnetic Materials Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201, China.
⁶ School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China.
⁷ State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083, China.
⁸ State Key Laboratory of Surface Physics and Department of Physics, Fudan University, Shanghai 200433, China.
⁹ NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg MD, 20899-6102, USA.
¹⁰ Institute of Solid State Chemistry, University of Science and Technology Beijing, Beijing 100083, China.

Abstract

Magnetic skyrmions are topologically protected quasiparticles that are promising for applications in spintronics. However, the low stability of most magnetic skyrmions leads to either a narrow temperature range in which they can exist, a low density of skyrmions, or the need for an external magnetic field, which greatly limits their wide application. In this study, high-density, spontaneous magnetic biskyrmions existing within a wide temperature range and without the need for a magnetic field were formed in ferrimagnets owing to the existence of a negative thermal expansion of the lattice. Moreover, a strong connection between the atomic-scale ferrimagnetic structure and nanoscale magnetic domains in Ho(Co,Fe)₃ was revealed via in situ neutron powder diffraction and Lorentz transmission electron microscopy measurements. The critical role of the negative thermal expansion in generating biskyrmions in HoCo₃ based on the magnetoelastic coupling effect is further demonstrated by comparing the behavior of HoCo_2.8Fe_0.2 with a positive thermal expansion.