Interfacial Magnetic Coupling Effects on the Magnetic and Magnetocaloric Properties of Rare Earth Element Doped LCMO-Mn₃O₄ Nanocomposites

Magnetic refrigeration technology, which works on the magnetocaloric effect (MCE) of magnetic materials, has attracted the interest of numerous research groups over traditional gas refrigeration. It has several advantages, including being highly energy-efficient, environmentally friendly, and cost-effective. The major effort is directed in improving the magnetic entropy change along with the relative cooling power (RCP) of oxide magnetocaloric materials. This study reports the synthesis and magnetocaloric properties of the novel rare earth element doped LCMO composites. These tetragonal crystal structure shaped compounds were synthesized with respect to AB₂O₇ type perovskite oxides with the <i>I4/mmm</i> group via the facile autocombustion technique. This rare earth europium element expanded the curie temperatures from La_1.4Ca_1.6Mn₂O₇ ~ 182 K to La_1.3Ca_1.6Eu_0.1Mn₂O₇ of ~ 186 K, which consequently enhanced the RCP value. 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 La_1.4Ca_1.6Mn₂O₇ and La_1.3Ca_1.6Eu_0.1Mn₂O₇ phases altered the double exchange interaction between Mn³⁺ and Mn⁴⁺ ions. The result do show that these interfacial disordered magnetic interactions of these nanocomposites further expanded the second order paramagnetic-to-ferromagnetic phase transition temperature up to 257 K at the temperature-dependent field-cooled magnetization curve which also led to enhance the change in magnitudes of magnetic entropy - △s to 0.52 J/kg/k under an applied magnetic field of 5T .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 Mn₃O₄ and LCMO nanocomposites.