Comprehensive study on effect of electron beam irradiation on electrical, thermo-electric and magnetic properties of oxygen rich LaMnO3.15 compound

Abstract

We report the influence of electron beam (EB) irradiation on the structural, electrical, thermoelectric and magnetic properties of oxygen rich LaMnO3 manganite. Refinement of XRD data shows that pristine as well irradiated samples are single phased and exhibit orthorhombic distorted structure (Pbnm) with the orthorhombic deformation slightly increasing with EB dosage. The MnO bond length increases with increase in EB dosage perhaps due to strain induced by EB irradiation. On contrary, the MnOMn bond angle remains unchanged for the irradiated samples. Electrical resistivity results shows that the small polaron hopping model is valid in the high temperature regime for all the samples. The pristine sample shows a small metal-insulator transition region around the characteristic temperature TMI, however EB irradiation induces a sharper metal-insulator transition behavior. The temperature dependence of Seebeck coefficient (S) of the pristine sample displays a crossover from positive to negative value as the sample is cooled whereas the irradiated samples exhibit only positive values. The Seebeck coefficient data is consistent with the resistivity data in the sense that the SPH model is valid in high temperature region. The magnetic measurements confirm the existence of short-range FM interaction above TC and all the samples follow Curie-Weiss law in the paramagnetic state.