Abstract
The coupling between lattice distortions and spin degrees of freedom provides a powerful pathway to control symmetry and emergent orders in quantum magnets. In this talk, I will demonstrate how uniaxial strain acts as a magnetoelastic tuning parameter that selectively breaks rotational symmetry and stabilizes new magnetic responses in two distinct material platforms. I will first present neutron-scattering studies of the van der Waals antiferromagnet FePSe3, where modest tensile strain detwins zigzag magnetic domains and induces pronounced C2-symmetric spin excitations. Strikingly, this symmetry breaking persists above the Néel temperature, providing direct microscopic evidence for vestigial three-state Potts nematicity driven by magnetoelastic coupling. I will then show that in the altermagnet candidate hexagonal FeS, in-plane compressive strain suppresses both the spontaneous anomalous Hall effect and the tiny c-axis ferromagnetic moment by tuning spin canting and magnetic domain populations, while leaving the primary antiferromagnetic structure intact. These results establish magnetoelastic control as a unifying framework for manipulating symmetry, spin excitations, and transport in quantum magnets, with broad implications for strain-engineered spintronic and topological functionalities.