Enhanced Exchange Bias in Epitaxial High-Entropy Oxide Heterostructures

Hailin Wang; Haoliang Huang; Yanpeng Feng; Yu-Chieh Ku; Cheng-En Liu; Shanquan Chen; Alan Farhan; Cinthia Piamonteze; Yalin Lu; Yunlong Tang; Jun Wei; Lang Chen; Chun-Fu Chang; Chang-Yang Kuo; Zuhuang Chen

doi:10.1021/acsami.3c14943

Enhanced Exchange Bias in Epitaxial High-Entropy Oxide Heterostructures

ACS Appl Mater Interfaces. 2023 Dec 20;15(50):58643-58650. doi: 10.1021/acsami.3c14943. Epub 2023 Dec 7.

Authors

Hailin Wang¹, Haoliang Huang^{2

3}, Yanpeng Feng⁴, Yu-Chieh Ku⁵, Cheng-En Liu⁵, Shanquan Chen¹, Alan Farhan⁶, Cinthia Piamonteze⁷, Yalin Lu², Yunlong Tang⁸, Jun Wei⁹, Lang Chen³, Chun-Fu Chang¹⁰, Chang-Yang Kuo^{5

11}, Zuhuang Chen^{1

9}

Affiliations

¹ School of Materials Science and Engineering, Harbin Institute of Technology, Shenzhen 518055, China.
² Anhui Laboratory of Advanced Photon Science and Technology & Hefei National Research Center for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China.
³ Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China.
⁴ Songshan Lake Materials Laboratory, Dongguan 523808, China.
⁵ Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu 30010, Taiwan.
⁶ Department of Physics, Baylor University, Waco, Texas 76798, United States.
⁷ Paul Scherrer Institut, Forschungstrasse 111, 5232 Villigen, Switzerland.
⁸ Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
⁹ Flexible Printed Electronics Technology Center, Harbin Institute of Technology, Shenzhen 518055, China.
¹⁰ Max-Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, 01187 Dresden, Germany.
¹¹ National Synchrotron Radiation Research Center, 101 Hsin-Ann Road, Hsinchu 30076, Taiwan.

PMID: 38062584
DOI: 10.1021/acsami.3c14943

Abstract

High-entropy oxides (HEOs) have gained significant interest in recent years due to their unique structural characteristics and potential to tailor functional properties. However, the electronic structure of the HEOs currently remains vastly unknown. In this work, combining magnetometry measurements, scanning transmission electron microscopy, and element-specific X-ray absorption spectroscopy, the electronic structure and magnetic properties of the perovskite-HEO La(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃ epitaxial thin films are systemically studied. It is found that enhanced magnetic frustration emerges from competing exchange interactions of the five transition-metal cations with energetically favorable half-filled/full-filled electron configurations, resulting in an unprecedented large vertical exchange bias effect in the single-crystalline films. Furthermore, our findings demonstrate that the La(Cr_0.2Mn_0.2Fe_0.2Co_0.2Ni_0.2)O₃ layer with a thickness down to 1 nm can be used as a pinning layer and strongly coupled with a ferromagnetic La_0.7Sr_0.3MnO₃ layer, leading to a notable exchange bias and coercivity enhancement in a cooling field as small as 5 Oe. Our studies not only provide invaluable insight into the electronic structure of HEOs but also pave the way for a new era of large bias materials for spintronics devices.

Keywords: epitaxial films; exchange bias effect; heterostructures; high-entropy oxides; perovskite oxide.