Topological surface magnetism and Néel vector control in a magnetoelectric antiferromagnet

• Published in: npj quantum materials Vol. 8; no. 1; pp. 17 - 8
• Main Authors: Du, Kai, Xu, Xianghan, Won, Choongjae, Wang, Kefeng, Crooker, Scott A., Rangan, Sylvie, Bartynski, Robert, Cheong, Sang-Wook
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 15-04-2023; Nature Publishing Group; Nature Portfolio
• Subjects: 639/766/119/1001; 639/766/119/544; 639/766/119/996; 639/766/119/997; Antiferromagnetism; Chromium oxides; Condensed Matter Physics; Electric fields; ferroelectrics and multiferroics; Magnetic fields; magnetic properties and materials; Magnetism; MATERIALS SCIENCE; Physics; Physics and Astronomy; Quantum Physics; Room temperature; Single crystals; spintronics; Structural Materials; Surfaces and Interfaces; surfaces, interfaces and thin films; Thin Films
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-023-00551-0

Antiferromagnetic states with no stray magnetic fields can enable high-density ultra-fast spintronic technologies. However, the detection and control of antiferromagnetic Néel vectors remain challenging. Linear magnetoelectric antiferromagnets (LMAs) may provide new pathways, but applying simultaneous electric and magnetic fields, necessary to control Néel vectors in LMAs, is cumbersome and impractical for most applications. Herein, we show that Cr
2
O
3
, a prototypical room-temperature LMA, carries a topologically-protected surface magnetism in all surfaces, which stems from intrinsic surface electric fields due to band bending, combined with the bulk linear magnetoelectricity. Consequently, bulk Néel vectors with zero bulk magnetization can be simply tuned by magnetic fields through controlling the magnetizations associated with the surface magnetism. Our results imply that the surface magnetizations discovered in Cr
2
O
3
should be also present in all LMAs.