Magnetic properties and magnetocaloric effects in Eu(Ti,Nb,Mn)O₃ perovskites

In perovskite EuTiO₃, the magnetic characteristics and magnetocaloric effect (MCE) can be flexibly regulated by converting the magnetism from antiferromagnetic to ferromagnetic. In the present work, a series of Eu(Ti,Nb,Mn)O₃ compounds, abbreviated as ETNMO for convenience of description, was fabricated and their crystallography, magnetism together with cryogenic magnetocaloric effects were systematically investigated. The crystallographic results demonstrate the cubic perovskite structure for all the compounds, with the space group of Pm3m. Two magnetic phase transitions are observed in these second-order phase transition (SOPT) materials. The joint substitution of elements Mn and Nb can considerably manipulate the magnetic phase transition process and magnetocaloric performance of the ETNMO compounds. As the Mn content increases, gradually widened –ΔS_M-T curves are obtained, and two peaks with a broad shoulder are observed in the –ΔS_M-T curves for Δμ₀H≤0–1 T. Under a field change of 0–5 T, the values of maximum magnetic entropy change (−ΔS_M^max) and refrigeration capacity (RC) are evaluated to be 34.7 J/(kg·K) and 364.9 J/kg for EuTi_0.8625Nb_0.0625Mn_0.075O₃, 27.8 J/(kg·K) and 367.6 J/kg for EuTi_0.8375Nb_0.0625Mn_0.1O₃, 23.2 J/(kg·K) and 369.2 J/kg for EuTi_0.8125Nb_0.0625Mn_0.125O₃, 17.1 J/(kg·K) and 357.6 J/kg for EuTi_0.7875Nb_0.0625Mn_0.15O₃, respectively. The considerable MCE parameters make the ETNMO compounds potential candidates for cryogenic magnetic refrigeration.