Unveiling Magnetic Frustration via the Elastocaloric Effect

Motivated by experimental progress in pressure and strain tuning of quantum materials, we examine the thermodynamic response of frustrated magnets to uniaxial strain. Specifically, we study Ising and Heisenberg models on spatially anisotropic triangular (and, for the Ising model, also kagome) lattices. We determine the entropy as a function of temperature and strain, and use it to compute the elastic Gr\"uneisen ratio $\eta$. The Ising models can be strain-tuned into and out of classical spin-liquid phases, and we show that $\eta$ can become arbitrarily large at low temperature $T$ near the point of maximal frustration, a universal hallmark of an extensive ground-state entropy. In contrast, the spin-$1/2$ Heisenberg model is moderately frustrated and displays multiple $T=0$ phase transitions. These transitions dominate $\eta$ at low $T$ while the intermediate-$T$ behavior is similar to that of the Ising model. We discuss the extent to which the elastic Gr\"uneisen ratio can be used to deduce the phase diagram, and we connect our results to recent experiments on triangular-lattice magnets.