Substitutional effects on structural and magnetotransport properties of La0.85-xSmxK0.15MnO3 (x=0.05, 0.1 and 0.15)

A series of polycrystalline La-0.85 xSmxK0.15MnO3 (x = 0.05, 0.1 and 0.15) have been synthesized by standard solid state reaction method to study effects of substituting La3+ by Sm3+ ion on the structural, electrical and magnetic properties. The Rietveld refinement of X-ray diffraction data revealed that mixed valence manganites crystallize in rhombohedral structure (space group R (3) over barC, no. 167). Raman spectra at room temperature reveal gradual change in phonon modes on increased doping. The temperature dependent electrical resistivity is measured by a standard four- probe method between 5 and 300 K. The temperature dependent electrical resistivity exhibits metal- insulator transition at temperature TMI and metallic state (T < T-MI) signifies importance of electron- electron, electron- phonon and electron- spin fluctuation scattering process. The peak resistivity qm increases rapidly with Sm and TMI shifts to a lower temperature. The high temperature (T > T-MI) conductivity data signifies polaronic nature. Application of magnetic field suppresses resistivity in entire temperature range. Low temperatures resistivity infers a field- dependent minimum and is due to electron- electron interaction and Kondo effects of mixed valence manganites. The ferro to paramagnetic transition temperature (TC) decreases with decreasing ionic radius as well as one- electron bandwidth of the A-site cation. (C) 2013 Elsevier B.V. All rights reserved.