Mixed rare earth oxides derived from monazite sand as an inexpensive precursor material for room temperature magnetic refrigeration applications

Abstract

An inexpensive perovskite type (REMIX)0.67Sr0.33MnO3 compound is synthesized via solid state method using mixed rare earth oxide precursor derived from monazite sand. Rietveld refinement of X-ray powder diffraction patterns confirms the compound is a mixture of rare earth manganites which is the major phase and CeO2 as the secondary phase. The compound shows a second order ferromagnetic to paramagnetic transition near room temperature and exhibits a magnetic entropy change (-ΔSM) of 3.28Jkg−1K−1 with a relative cooling power (RCP) of 120Jkg−1 and an adiabatic temperature change (ΔTad) of 2.11K at 310K under 50kOe magnetic field. The Debye temperature of the compound is found to be 543K and room temperature thermal conductivity is 4.26Wm−1K−1. The temperature variation of electrical resistivity shows a metal to insulator transition around 180K, which gets shifted towards higher temperature upon the application of magnetic field. The compound shows a large value of −ΔSM and this work makes an endeavor to develop low–cost materials for the magnetic refrigeration applications near the room temperature.