Air-Stable and Layer-Dependent Ferromagnetism in Atomically Thin van der Waals CrPS4

Joolee Son; Suhan Son; Pyeongjae Park; Maengsuk Kim; Zui Tao; Juhyun Oh; Taehyeon Lee; Sanghyun Lee; Junghyun Kim; Kaixuan Zhang; Kwanghee Cho; Takashi Kamiyama; Jun Hee Lee; Kin Fai Mak; Jie Shan; Miyoung Kim; Je-Geun Park; Jieun Lee

doi:10.1021/acsnano.1c07860

Air-Stable and Layer-Dependent Ferromagnetism in Atomically Thin van der Waals CrPS₄

ACS Nano. 2021 Oct 26;15(10):16904-16912. doi: 10.1021/acsnano.1c07860. Epub 2021 Oct 18.

Authors

Joolee Son^{1

2}, Suhan Son^{1

3

4}, Pyeongjae Park^{1

3

4}, Maengsuk Kim⁵, Zui Tao⁶, Juhyun Oh⁷, Taehyeon Lee¹, Sanghyun Lee⁸, Junghyun Kim^{1

3

4}, Kaixuan Zhang^{1

3

4}, Kwanghee Cho⁹, Takashi Kamiyama⁹, Jun Hee Lee⁵, Kin Fai Mak⁶, Jie Shan⁶, Miyoung Kim⁷, Je-Geun Park^{1

3

4}, Jieun Lee^{1

2}

Affiliations

¹ Institute of Applied Physics and Department of Physics and Astronomy, Seoul National University, Seoul 08826, Korea.
² Department of Physics and Department of Energy Systems Research, Ajou University, Suwon 16499, Korea.
³ Center for Quantum Materials, Seoul National University, Seoul 08826, Korea.
⁴ Center for Correlated Electron Systems, Institute for Basic Science, Seoul 08826, Korea.
⁵ School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology, Ulsan 44919, Korea.
⁶ Department of Physics and School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14850, United States.
⁷ Department of Materials Science and Engineering and Research Institute of Advanced Materials, Seoul National University, Seoul 08826, Korea.
⁸ LG Chem Research Park, Daejeon 34122, Korea.
⁹ Materials and Life Science Division, J-PARC Center, Japan Atomic Energy Agency, Tokai 319-1195, Japan.

PMID: 34661389
DOI: 10.1021/acsnano.1c07860

Abstract

Ferromagnetism in two-dimensional materials presents a promising platform for the development of ultrathin spintronic devices with advanced functionalities. Recently discovered ferromagnetic van der Waals crystals such as CrI₃, readily isolated two-dimensional crystals, are highly tunable through external fields or structural modifications. However, there remains a challenge because of material instability under air exposure. Here, we report the observation of an air-stable and layer-dependent ferromagnetic (FM) van der Waals crystal, CrPS₄, using magneto-optic Kerr effect microscopy. In contrast to the antiferromagnetic (AFM) bulk, the FM out-of-plane spin orientation is found in the monolayer crystal. Furthermore, alternating AFM and FM properties observed in even and odd layers suggest robust antiferromagnetic exchange interactions between layers. The observed ferromagnetism in these crystals remains resilient even after the air exposure of about a day, providing possibilities for the practical applications of van der Waals spintronics.

Keywords: CrPS4; air stability; ferromagnetism; magneto-optic Kerr effect; van der Waals material.