Observance of Improved Magneto-resistance and Magnetic Entropy Change in La0.7(Ca0.2Sr0.1)MnO3:Pd Composite

Abstract

Magneto-resistive and magneto-caloric properties of polycrystalline La 0.7 (Ca 0.2 Sr 0.1 )MnO 3 (LCSMO) and La 0.7 (Ca 0.2 Sr 0.1 )MnO 3 :10 %PdO (LCSMO:Pd10) composites sintered at 1400 • C have been investigated. Rietveld refinement of their X-ray diffraction (XRD) patterns confirms the single-phase crystalline structure with orthorhombic Pbnm space group, showing no significant change in their lattice parameters with Pd addition. Disappearance of the low temperature resistivity hump in the Pd composite has been attributed to the suppression of the grain boundary effect and the conducting channels due to the presence of metallic Pd. While the Curie temperature T c remained nearly unchanged, the peak value of the temperature coefficient of resistance (TCR) increased in the composite. TCR MAX increased to 6.4 % (at 308 K) in the composite from 2 % (at 305 K) for the pristine LCSMO. Magnetoresistance (MR) and magnetic entropy change ( S M ) also increased markedly in the composite material. This could be ascribed to the observed sharpness of both the magnetic and resistive transitions resulting from better grain connectivity. Maximum MR of 12.9 % (1 T) and 19.6 % (2 T) has been observed close to its T c (309 K) in the pristine LCSMO. These values increased to 24.1 % (1 T) and 33.9 % (2 T) with the addition of PdO.