Highly Anisotropic Mechanical Response of the Van der Waals Magnet CrPS₄

Abstract

Semiconducting van der Waals magnets exhibit a rich physical phenomenology with different collective excitations, as magnons or excitons, that can be coupled, thereby offering new opportunities for optoelectronic, spintronic, and magnonic devices. In contrast with the well‐studied van der Waals magnets CrI3 or Fe3GeTe2, CrPS4 is a layered metamagnet with a high optical and magnon transport anisotropy. Here, the structural anisotropy of CrPS4 above and below the magnetic phase transition is investigated by fabricating nanomechanical resonators. A large anisotropy is observed in the resonance frequency of resonators oriented along the crystalline a‐ and b‐axis, indicative of a lattice expansion along the b‐axis, boosted at the magnetic phase transition, and a rather small continuous contraction along the a‐axis. This behavior in the mechanical response differs from that previously reported in van der Waals magnets, as FePS3 or CoPS3, and can be understood from the quasi‐1D nature of CrPS4. The results pinpoint CrPS4 as a promising material in the field of low‐dimensional magnetism and show the potential of mechanical resonators for unraveling the in‐plane structural anisotropy coupled to the magnetic ordering that, in a broader context, can be extended to studying structural modifications in other 2D materials and van der Waals heterostructures.