Tailored cryogenic magnetism and magnetocaloric effect in EuTi_1-xTa_xO₃ perovskites

Rare-earth-based oxides are gradually becoming a new research hotspot in cryogenic magnetic refrigeration due to their advantages in bulk preparation and application. Magnetic transition from AFM to FM in EuTiO₃ provides an effective strategy for modulating magnetism and enhancing magnetocaloric effect (MCE) in this magnetic system. Herein the structure, magnetism, and MCE of a series of Ta-doped EuTiO₃ perovskites were investigated in detail. A significant lattice expansion was achieved by partially substituting Ta for B-site Ti without altering the crystal configuration, which tailors the cryogenic magnetism and MCEs of these compounds. Lattice expansion enhances ferromagnetic coupling, weakens antiferromagnetic super-exchange, and promotes the AFM-FM transition in EuTiO₃, which enhances the low-field MCEs. The phase transition temperature of the compound increases from 5.5 K to about 9.5 K with increasing Ta doping. The values of −ΔS_M^max and RC of EuTi_0.9375Ta_0.0625O₃ are 15.9 J kg⁻¹ K⁻¹and 67.8 J kg⁻¹ under magnetic field change of 0–1 T, which are enhanced by 44.5% and 105.5% over EuTiO₃, respectively. Although a decrease in the magnetic entropy change occurs with increasing Ta doping, the refrigerating capacity is improved due to the broadened temperature range. This work not only provides a strategy for tailoring magnetic phase transition and MCE of magnetocaloric materials, but also offers effective candidates for magnetic refrigeration over a wide temperature range.