Tailored cryogenic magnetism and magnetocaloric effect in EuTi1-xTaxO3 perovskites

Abstract

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 −ΔSMmax and RC of EuTi0.9375Ta0.0625O3 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.