Abstract: Refrigeration in the liquid helium temperature range provides vital technological support for many scientific frontiers and engineering technologies. The considerable magnetocaloric effect (MCE) makes EuTiO₃ a potential candidate for magnetic refrigeration near liquid helium temperature. More interestingly, the magnetic transition from antiferromagnetism to ferromagnetism offers the possibility to tailor the magnetism and improve the MCE of this magnetic system. In this study, the magnetic properties and MCE of EuTi_0.875Zr_0.125O₃ were systematically investigated by first-principles calculation and experiments. The substitution of Zr induces a significant lattice expansion and alters the electronic interactions, leading to a dominance of ferromagnetism in the compound. Remarkable low-field MCE performance has been achieved attributed to the enhanced ferromagnetism and low saturation field. Under the field change of 0-1 T, the maximum magnetic entropy change ($-\Delta S_{M}^{\max }$) and adiabatic temperature change ($\Delta T_{a d}^{\max }$) are 17.9 J kg^-1 K^-1 and 6.1 K, respectively. It is worth noting that the $-\Delta S_{M}^{\max }$ of EuTi_0.875Zr_0.125O₃ reaches 10.3 J kg^-1 K^-1 for a field change of 0-0.5 T, making it one of the best magnetocaloric materials ever reported operating in the liquid helium temperature range.

Key words: Magnetic properties, Magnetocaloric effect, EuTi_0.875Zr_0.125O₃, Ferromagnetism, Magnetic refrigeration