Spin-Orbit-Induced Ising Ferromagnetism at a van der Waals Interface.

Matsuoka, Hideki; Barnes, Stewart Edward; Ieda, Jun'ichi; Maekawa, Sadamichi; Bahramy, Mohammad Saeed; Saika, Bruno Kenichi; Takeda, Yukiharu; Wadati, Hiroki et al. · Nano Lett · 2021

basic_science · Level V

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Abstract

Magnetocrystalline anisotropy, a key ingredient for establishing long-range order in a magnetic material down to the two-dimensional (2D) limit, is generally associated with spin-orbit interaction (SOI) involving a finite orbital angular momentum. Here we report strong out-of-plane magnetic anisotropy without orbital angular momentum, emerging at the interface between two different van der Waals (vdW) materials, an archetypal metallic vdW material NbSe<sub>2</sub> possessing Zeeman-type SOI and an isotropic vdW ferromagnet V<sub>5</sub>Se<sub>8</sub>. We found that the Zeeman SOI in NbSe<sub>2</sub> induces robust out-of-plane magnetic anisotropy in V<sub>5</sub>Se<sub>8</sub> down to the 2D limit with a more than 2-fold enhancement of the transition temperature. We propose a simple model that takes into account the energy gain in NbSe<sub>2</sub> in contact with a ferromagnet, which naturally explains our observations. Our results demonstrate a conceptually new magnetic proximity effect at the vdW interface, expanding the horizons of emergent phenomena achievable in vdW heterostructures.