Probing ultraweak in-plane magnetic anisotropy within a two-dimensional layered antiferromagnet.

Fan, Yijie; Xu, Yihong; Bian, Renji; Zhang, Ruan; Mei, Junning; Wu, Jiaxin; Xie, Binghe; Zhu, Shuangxing et al. · Proc Natl Acad Sci U S A · 2025

basic_science · Level V

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Abstract

Magnetic anisotropy plays a crucial role in determining the critical behavior and phase transitions in two-dimensional magnetic systems. It is also required for the design of thin-film spintronic devices. Despite its significance, sensing extremely weak anisotropy has proven challenging in van der Waals antiferromagnetic/ferrimagnetic materials. Here, we first employ simulations of micromagnetic energy function in few-layer easy-plane antiferromagnetic systems with a weak additional uniaxial anisotropy and unveil an intriguing even-odd effect closely linked to low-field spin-flop behaviors. We further perform tunneling magneto-conductance measurements on a model 2D antiferromagnetic insulator, CrCl<sub>3</sub>, exhibiting near-ideal easy-plane anisotropy. The magnetic field-controlled tunneling current at low temperature aligns well with simulated in-plane anisotropic spin-configuration, providing direct experimental evidence for detecting magnetic anisotropy field around 1 mT. Our work creates opportunities for finely characterizing magnetic structures and behaviors in 2D antiferromagnetic/ferrimagnetic systems, with potential applications in spintronics such as data storage and magnetic sensing.