Exchange Bias Effect in Ferro-/Antiferromagnetic van der Waals Heterostructures.

Srivastava, Pawan Kumar; Hassan, Yasir; Ahn, Hyobin; Kang, Byunggil; Jung, Soon-Gil; Gebredingle, Yisehak; Joe, Minwoong; Abbas, Muhammad Sabbtain et al. · Nano Lett · 2020

basic_science · Level V

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Abstract

The recent discovery of magnetic van der Waals (vdW) materials provides a platform to answer fundamental questions on the two-dimensional (2D) limit of magnetic phenomena and applications. An important question in magnetism is the ultimate limit of the antiferromagnetic layer thickness in ferromagnetic (FM)/antiferromagnetic (AFM) heterostructures to observe the exchange bias (EB) effect, of which origin has been subject to a long-standing debate. Here, we report that the EB effect is maintained down to the atomic bilayer of AFM in the FM (Fe<sub>3</sub>GeTe<sub>2</sub>)/AFM (CrPS<sub>4</sub>) vdW heterostructure, but it vanishes at the single-layer limit. Given that CrPS<sub>4</sub> is of A-type AFM and, thus, the bilayer is the smallest unit to form an AFM, this result clearly demonstrates the 2D limit of EB; only one unit of AFM ordering is sufficient for a finite EB effect. Moreover, the semiconducting property of AFM CrPS<sub>4</sub> allows us to electrically control the exchange bias, providing an energy-efficient knob for spintronic devices.