Interface driven electrical and magneto-transport properties of (100 – x )% La 0.7 Sr 0.3 MnO 3 – x % Paraffin wax (0 ≤ x ≤ 1) hybrid nanocomposites

We report electrical and magneto-transport properties of La0.7 Sr0.3 MnO3 (LSMO)/Paraffin wax nanocomposites prepared through low temperature chemical pyrophoric reaction process. A core shell structure is expected to be formed having a ferromagnetic LSMO core and a spin disordered shell of paraffin wax. Enhanced charging energy due to coulomb blockade contribution with increasing paraffin wax is observed for the composites attributing enhanced intergranular distance between LSMO grains. Effective spin-polarized tunneling of conduction electrons resulting in sharp low field magnetoresistance (MR) of the composites is due to reordering of spin disorder at paraffin wax shell with magnetic field. Moreover, observation of enhanced magnetoresistive hysteresis with decrease in temperature has been attributed to increased blocked states at LSMO grain surface. Calculated surface spin susceptibility (χ b ) has been found to follow similar behavior of MR with temperature indicating surface magnetization dependent MR. Fitting of magnetoconductance versus field curves reveal increase of Para to ferro transition temperature, T C and χ b indicate higher antiferromagnetic coupling of shell spins for composite samples than pristine LSMO above 50 K. χ b also indicate systematic decrease in surface spin disorder of the composite samples with respect to pure LSMO which is expected to be due to the probable covalent bond formation between Paraffin wax molecules and surface atoms of LSMO nanoparticles.