Magnetocaloric properties of rare-earth element doped LCMO-Mn3O4 nanocomposites

Abstract

The study reports the synthesis and magnetocaloric properties of the rare-earth element as Eu3+ doped La1.4Ca1.6Mn2O7-Mn3O4 composites prepared by the one-pot autocombustion technique. Eu3+ co-doping enhanced the Curie temperatures from 181 K for La1.4Ca1.6Mn2O7 (LCMO) to 186 K for La1.3Ca1.6Eu0.1Mn2O7 perovskites, which consequently enhanced the relative cooling power value of the compound. Moreover, these composites were also prepared in the presence of 10 wt% of Mn3O4 nanoparticles. The presence of Mn3O4 at the intervening grain boundaries between La1.4Ca1.6Mn2O7 (A) and La1.3Ca1.6Eu0.1Mn2O7 (B) phases altered the double exchange interaction between Mn3+ and Mn4+ ions. The temperature-dependent field-cooled magnetization curves showed that these nanocomposites’ interfacial magnetic interactions significantly expanded the second-order ferromagnetic-to-paramagnetic phase transition temperature. This further enhanced the magnetic entropy magnitudes |ΔSMax| up to 0.521 J kg−1 k−1 and the associated relative cooling power value to 43.67 J kg−1 under a 5T applied magnetic field. The temperature-averaged entropy change (TEC) values of composites outperformed the individual values of samples A and B between the temperature range of 80–240 K. The fundamental key of this work is to demonstrate the potentiality of enhancing the magnetic phase transition temperature and magnetocaloric effect in the framework of interfacial coupling between LCMO and the Mn3O4 phases of the nanocomposites.