Large magneto-optical Kerr effect and imaging of magnetic octupole domains in an antiferromagnetic metal

Tomoya Higo; Huiyuan Man; Daniel B Gopman; Liang Wu; Takashi Koretsune; Olaf M J van 't Erve; Yury P Kabanov; Dylan Rees; Yufan Li; Michi-To Suzuki; Shreyas Patankar; Muhammad Ikhlas; C L Chien; Ryotaro Arita; Robert D Shull; Joseph Orenstein; Satoru Nakatsuji

doi:10.1038/s41566-017-0086-z

Large magneto-optical Kerr effect and imaging of magnetic octupole domains in an antiferromagnetic metal

Nat Photonics. 2018 Feb;12(2):73-78. doi: 10.1038/s41566-017-0086-z. Epub 2018 Jan 26.

Authors

Tomoya Higo^{1

2}, Huiyuan Man¹, Daniel B Gopman³, Liang Wu^{4

5

6}, Takashi Koretsune^{2

7

8}, Olaf M J van 't Erve⁹, Yury P Kabanov^{3

10}, Dylan Rees^{4

5}, Yufan Li¹¹, Michi-To Suzuki^{2

8}, Shreyas Patankar^{4

5}, Muhammad Ikhlas^{1

2}, C L Chien¹¹, Ryotaro Arita^{2

8}, Robert D Shull³, Joseph Orenstein^{4

5}, Satoru Nakatsuji^{1

2}

Affiliations

¹ Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
² CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 332-0012, Japan.
³ Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899, USA.
⁴ Department of Physics, University of California, Berkeley, California 94720, USA.
⁵ Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
⁶ Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
⁷ Department of Physics, Tohoku University, Sendai, Miyagi 980-8578, Japan.
⁸ RIKEN-CEMS, Wako, Saitama 351-0198, Japan.
⁹ Materials Science and Technology Division, U.S. Naval Research Laboratory, Washington, DC 20375, USA.
¹⁰ Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region 142432, Russia.
¹¹ Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA.

Abstract

When a polarized light beam is incident upon the surface of a magnetic material, the reflected light undergoes a polarization rotation¹. This magneto-optical Kerr effect (MOKE) has been intensively studied in a variety of ferro- and ferrimagnetic materials because it provides a powerful probe for electronic and magnetic properties^{2, 3} as well as for various applications including magneto-optical recording⁴. Recently, there has been a surge of interest in antiferromagnets (AFMs) as prospective spintronic materials for high-density and ultrafast memory devices, owing to their vanishingly small stray field and orders of magnitude faster spin dynamics compared to their ferromagnetic counterparts^5-9. In fact, the MOKE has proven useful for the study and application of the antiferromagnetic (AF) state. Although limited to insulators, certain types of AFMs are known to exhibit a large MOKE, as they are weak ferromagnets due to canting of the otherwise collinear spin structure^10-14. Here we report the first observation of a large MOKE signal in an AF metal at room temperature. In particular, we find that despite a vanishingly small magnetization of M ~0.002 µ_B/Mn, the non-collinear AF metal Mn₃Sn¹⁵ exhibits a large zero-field MOKE with a polar Kerr rotation angle of 20 milli-degrees, comparable to ferromagnetic metals. Our first-principles calculations have clarified that ferroic ordering of magnetic octupoles in the non-collinear Néel state¹⁶ may cause a large MOKE even in its fully compensated AF state without spin magnetization. This large MOKE further allows imaging of the magnetic octupole domains and their reversal induced by magnetic field. The observation of a large MOKE in an AF metal should open new avenues for the study of domain dynamics as well as spintronics using AFMs.

Grants and funding

9999-NIST/Intramural NIST DOC/United States