Giant Room-Temperature Magnetocaloric Effect in Two-Dimensional Ternary Transition Metal Chalcogenides

We investigate the magnetic exchange interaction, magnetic anisotropy (MAE), and magnetocaloric effect (MCE) of ternary transition metal chalcogenides A₂MX₄ (A = Ti or V; M = W or Mo; X = S or Se). We find that Ti₂WS₄ and Ti₂WSe₄ exhibit large entropy changes of 5.97 and 5.51 μJ m⁻² K⁻¹, respectively, under a magnetic field near room temperature. Analysis based on perturbation theory indicates that strong second-nearest-neighbor exchange coupling plays an important role in MCE, along with a large MAE of ∼10 meV that is attributed to the coupling contributions of dx²-y² and dz² orbitals of the W atom. Moreover, strain and carrier doping effectively modulate the MAE and Curie temperature, leading to remarkable enhancement of the MCE. This work provides important insights into the design of two-dimensional materials with enhanced MCE and is expected to facilitate further advancements in room-temperature magnetic refrigeration for practical applications.