Structural, dielectric and magnetocaloric properties ofLa1-xSrxMnO3 (x = 0.2, 0.3, 0.4) perovskite manganite

Abstract

The effects of Sr substitution on the structural, dielectric, magnetic and magnetocaloric properties of LaMnO¬3 perovskite manganite having the compositions La1-xSrxMnO3 (x = 0.2, 0.3 and 0.4) along with the microstructural feature are reported in this study. The samples were prepared by solid state reaction technique. The structural property has been studied with an X-ray diffraction technique, which indicates that all the prepared samples have shown a rhombohedral structure. Frequency dependent dielectric constant (ε') of La1-xSrxMnO3 has been measured at room temperature. It demonstrates that ε^' decreases with increasing frequency which follows the Maxwell-Wagner polarization model. The values of Curie temperature (Tc) and saturation magnetization (Ms) decrease as the Sr content increases from x = 0.2 to x = 0.3 due to the dominating of grain size effect over the double exchange interaction and the reduction of grain size, respectively. Both Tc and Ms increase from x = 0.3 to 0.4 which may be attributed to the stronger of double exchange interaction and the increase in grain diameter along with the densification of the sample, respectively. The magnetocaloric effect has been investigated in terms of the change in entropy (∆S_m) and relative cooling power (RCP) factor. The value of Tc is about 312 K (at x = 0.3), which is near to room temperature. The values of (〖ΔS〗_m )_max are found to be 1.031 and 2.245 J/(kg. K), and the values of RCP are found to be 95 and 278 J/K (at x = 0.3) for H = 2 and 5 T, respectively. From the observed values of magnetocaloric properties, it can be inferred that La0.7Sr0.3MnO3 can be considered as an attractive material for magnetic refrigeration application.