[18p-Z31-1~19] 17.3 Layered materials

▲ [18p-Z31-1] Thickness dependence of ferromagnetism in Cr₃Te₄ epitaxial thin films grown by molecular beam epitaxy

〇Yue Wang¹, Shun Kajihara¹, Masaki Nakano^1,2, Satoshi Yoshida¹, Hideki Matsuoka¹, Kyoko Ishizaka^1,2, Yoshihiro Iwasa^1,2 (1.Dept. Appl. Phys., Univ. Tokyo, 2.RIKEN CEMS)

Keywords:2D materials, Transition-metal dichalcogenide, Molecular-beam epitaxy

The discoveries of intrinsic ferromagnetism in atomically-thin van der Waals crystals have opened up a new research field enabling fundamental studies on magnetism at two dimensional (2D) limit as well as development of magnetic van der Waals heterostructures. To date, a variety of 2D ferromagnetism has been explored with different electronic properties, such as insulating ferromagnets Cr₂Ge₂Te₆ and CrI₃ , and metallic ferromagnet Fe₃GeTe₂ and V₅Se₈. However, 2D ferromagnets with high Curie temperature (T_C) was still missing, until recent discovery of room temperature ferromagnetism in monolayer VSe₂, although there have been many discussions and enigma on the origin of its ferromagnetism. One promising candidate is chromium telluride, which has been known to possess T_C ranging from 220 K to 340 K depending on the chromium intercalation level. Recently we have succeeded in growing atomically-thin chromium telluride epitaxial thin films on insulating sapphire substrates by molecular beam epitaxy (MBE), and identified its phase as Cr₃Te₄ based on the detailed analysis on the structural and magnetic properties. We found that T_C of the as-grown samples were about 160 K, but it increased up to 310 K by post-growth annealing. Moreover, very interestingly, we found that those with- and without-annealing samples show different thickness dependence of T_C. In this presentation, we will discuss those results in detail.