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

Abstract

A series of polycrystalline La0.85−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 R3¯C, 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 300K. The temperature dependent electrical resistivity exhibits metal–insulator transition at temperature TMI and metallic state (T<TMI) signifies importance of electron–electron, electron–phonon and electron–spin fluctuation scattering process. The peak resistivity ρm increases rapidly with Sm and TMI shifts to a lower temperature. The high temperature (T>TMI) 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.