Enhanced magnetocaloric effect driven by interfacial magnetic coupling in self-assembled Mn₃O₄-La_0.7Sr_0.3MnO₃ nanocomposites

Magnetic refrigeration, resulting from the magnetocaloric effect of a material around the magnetic phase-transition temperature, is a topic of great interest as it is considered to be an alternate energy solution to conventional vapor-compression refrigeration. The viability of a magnetic refrigeration system for magnetic cooling can be tested by exploiting materials in various forms, from bulk to nanostrucutres. In this study, magnetocaloric properties of self-assembled Mn₃O₄-La_0.7Sr_0.3MnO₃ nanocomposites, with varying doping concentrations of Mn₃O₄ in the form of nanocrystals embedded in the La_0.7Sr_0.3MnO₃ matrix, are investigated. The temperatures corresponding to the paramagnetic-to-ferromagnetic transitions are higher, and the values of change in magnetic entropy under a magnetic field of 2 T show an enhancement (highest being ∼130%) for the nanocomposites with low doping concentrations of Mn₃O₄, compared to that of pure La_0.7Sr_0.3MnO₃ thin films. Relative cooling power remain close to those of La_0.7Sr_0.3MnO₃. The enhanced magnetic phase-transition temperature and magnetocaloric effect are interpreted and evidenced in the framework of interfacial coupling between Mn₃O₄ and La_0.7Sr_0.3MnO₃. This work demonstrates the potentiality of self-assembled nanostructures for magnetic cooling near room temperature under low magnetic fields.