Impact of sintering temperature on room temperature magneto-resistive and magneto-caloric properties of Pr_(2/3)Sr_(1/3)MnO_3

摘要

Magneto-resistive and magneto-caloric properties of polycrystalline Pr_(2/3)Sr_(1/3)MnO_3 have been studied as a function of sintering temperature (T_s) between 1260 and 1450 °C. Reitveld refinement of their X-ray diffraction (XRD) patterns confirms their single phase crystalline structure with orthorhombic Pbnm space group. The point of maximum value of temperature coefficient of resistance (TCR_(max)) and Curie temperature (T_c) decreased slightly with T_s. Magneto-resistance (MR) and magnetic entropy (ΔS_M) increased markedly with sintering temperature. This could be attributed to the observed sharpness of both the magnetic and resistive transitions due to better grain connectivity. Optimum results are obtained for the sample with T_s = 1400 °C. MR at T_c of the same is found to be as large as 32% at 1T and 58% at 5T magnetic fields. The maximum entropy change (ΔS_Mmax) near its T_c is 2.3Jkg~(-1) K~(-1) and 7.8J kg~(-1) K~(-1) upon 1T and 5T fields change respectively. These characteristics [MR (32% 1T, 58% 5T) and reasonable change in magnetic entropy (7.8 J kg~(-1)K~(-1) 5T)] generate possibility that the optimized compound can be used as a potential magnetic refrigerant close to room temperature.