Superexchange antiferromagnetism and cryogenic magnetocaloric effect in scheelite-type GdTi_0.5Mo_0.5O₄ compound

Scheelite-type LnLiF₄ compounds have become promising cryogenic magnetic refrigerants due to their giant low-field magnetocaloric effect (MCE). This work presents an example of a scheelite-type rare-earth transition metal oxide GdTi_0.5Mo_0.5O₄. The magnetic interactions, magnetic phase transition (MPT) and MCE of GdTi_0.5Mo_0.5O₄ compound were investigated through magnetization measurements and a mean-field approach. A mean-field model was used to elucidate the role of primarily superexchange antiferromagnetic (AFM) coupling on the magnetocaloric performance in this compound. From the analysis of the magnetization dependence, an isotropic AFM exchange coupling with energy scale ε_ex = J_nnS² ≈ 1.7 K was estimated. The magnetic susceptibility reveals the occurrence of MPT from paramagnetic (PM) to AFM at the Néel temperature (T_N ≈ 1.3 K). GdTi_0.5Mo_0.5O₄ exhibits a large magnetic entropy change up to 43.3 J/(kg·K) at 1.3 K for μ₀ΔH = 0−7 T, which makes it a cryogenic magnetic refrigerant with potential applications. Furthermore, a mean-field model with superexchange AFM above 3 K can well predict the MCE observed in GdTi_0.5Mo_0.5O₄.