YRLG Workshop: Correlation and Topology in magnetic materials, July 16th - 18th 2024
Andriani Vervelaki
Two-dimensional (2D) magnets are an emerging area of research with potential for the development of magnetic materials and device applications ranging from magnetic storage to spintronics [1,2]. In contrast to conventional magnets, the magnetic properties of these materials respond sensitively to external stimuli, such as strain or doping. Engineering van der Waals (vdW) heterostructures from such 2D magnets can yield complex magnetic ground states including skyrmion phases or other non-collinear magnetic configurations [3].
The 2D semiconductor CrSBr is an A-type antiferromagnet with remarkable stability under ambient conditions and a Néel temperature of TN~132 K in the bulk [4]. Recently, a controllable and reversible strain-induced antiferromagnetic (AFM) to ferromagnetic (FM) phase transition was reported in CrSBr [5], suggesting the possibility of devices such as magnetoresistive switches that are actuated by strain or magnetic tunnel junctions that do not require an external applied field. The observed effect is attributed to changes in the magnetic exchange pathways that result in enhancement of the AFM interlayer interaction under compressive strain or decrease and eventually change of the AFM coupling to FM under tensile strain [5-6]. However, direct evidence of the influence of strain on the magnetic behavior and the effects of inhomogeneous strain in the material are not captured by the measurement techniques that have been used so far.
In this talk, I will present nanometer-scale magnetic imaging experiments, using our recently developed scanning SQUID-on-lever probe [7], that shed light on how strain affects the local magnetic behavior of the flake. We measure exfoliated flakes of CrSBr, in which strain has been induced along the a-axis by bending. As a result, spatially dependent compressive and tensile strain of varying strengths is produced on the same flake [8]. I will discuss how this inhomogeneous strain affects the magnetic hysteresis and the magnetic switching of the material when we apply an external magnetic field along the easy axis (b-axis). By performing micromagnetic simulations, we are able to reproduce the magnetic evolution and gain further insight into the underlying magnetization configurations.
[1] C. Gong et al. Nature 546 (2017), 265–269. [2] B. Huang et al. Nature 546 (2017), 270–273. [3] Y. Xu et al. Nat. Nanotechnol. 17 (2022), 143–147. [4] O. Göser et al. Journal of Magnetism and Magnetic Materials 92 (1990), 129-136. [5] J. Cenker et al. Nat. Nanotechnol. 17 (2022), 256-261. [6] X. Bo et al. New J. Phys. 25 (2023), 013026. [7] Wyss et al, Phys. Rev. Applied 17 (2022), 034002 [8] M. Kapfer et al. Science 381 (2023), 677-681.