Enhanced low-field magnetocaloric effect in Nb and Al co-substituted EuTiO3 compounds

Abstract

• First-principle calculations indicate that Nb and Al co-substitution can significantly enhance the FM coupling in Eu(Ti,Nb,Al)O 3 system. • The ground state of EuTi 0.875 Nb 0.0625 Al 0.0625 O 3 , EuTi 0.8125 Nb 0.125 Al 0.0625 O 3 and EuTi 0.75 Nb 0.125 Al 0.125 O 3 exhibit FM, which is consistent with the theoretical calculations. • In a field change of 0-1 T, the magnetic entropy change of all compounds is larger than 15 J•kg −1 •K −1 , and the maximum refrigeration capacity reaches 88 J•kg −1 . • Element co-substitution is proved to be an effective way to improve magnetocaloric effect. The magnetic ground state switching between antiferromagnetic (AFM) and ferromagnetic (FM) states in EuTiO 3 provides the feasibility of regulating its magnetic properties and magnetocaloric effect. First-principles calculations demonstrate that the magnetic ground states for EuTi 0.875 Nb 0.0625 Al 0.0625 O 3 , EuTi 0.8125 Nb 0.125 Al 0.0625 O 3 , and EuTi 0.75 Nb 0.125 Al 0.125 O 3 are FM coupling. Experimental results also exhibit the FM coupling domination in these compounds, accompanied by a significantly enhanced low magnetic field magnetocaloric effect. The maximum magnetic entropy change of all the samples surpasses 15 J kg −1 K −1 with a field change of 1 T, which is 1.4 times as large as that of bulk EuTiO 3 . Especially, the maximum refrigerating capacity for EuTi 0.8125 Nb 0.125 Al 0.0625 O 3 compound is evaluated to be 88.1 J kg −1 , more than three times of that of EuTiO 3 . The remarkable magnetocaloric performances prove Nb and Al co-substituted EuTiO 3 compounds to be competitive candidates for magnetic refrigeration in the liquid helium temperature regime.