Large Magnetocaloric Effect and Adiabatic Temperature Change in the Tellurate: Gd2TeO6
We investigate the structural, magnetic, thermodynamic, and magnetocaloric properties of polycrystalline Gd2TeO6, a rare-earth tellurate unexplored for cryogenic magnetic refrigeration. Powder X-ray diffraction confirms single-phase orthorhombic symmetry (P212121), featuring two crystallographically distinct seven-coordinate Gd sites. Magnetization measurements reveal no conventional long-range magnetic ordering down to 2 K, although low-field magnetic irreversibility emerges below approximately 4 K. Curie-Weiss analysis yields a Weiss temperature of -1.25 K, indicating weak predominantly antiferromagnetic interactions. The magnetization reaches approximately 97% of the theoretical saturation moment at 7 T with negligible hysteresis. Heat-capacity measurements reveal no sharp zero-field anomaly above 2 K, while a broad field-induced maximum indicates redistribution of low-energy magnetic entropy. Debye-Einstein analysis separates the lattice and magnetic contributions. At 2.5 K, the maximum magnetic entropy changes (-DeltaSM) reach 21.40, 48.51, and 54.81 J kg-1 K-1 for field changes of 0-2, 0-5, and 0-7 T, respectively. The corresponding volumetric entropy change reaches 400.50 mJ cm-3 K-1. Measurements up to 14 T yield (-DeltaSM) = 63.51 J kg-1 K-1, approaching the theoretical limit of 64.25 J kg-1 K-1. The estimated adiabatic temperature change is approximately 22.7 K for 0-7 T. First-principles calculations with GGA+U approximation reveal competing antiferromagnetic states, highlighting Gd2TeO6 as a promising candidate for cryogenic magnetocaloric applications.