Transport and Magnetic Properties of La_(0.85)Ca_(0·15)Mn_(1-x)Al_xO3 Manganites

摘要

We present here, the effect of Al doping on structural, electrical and magnetic properties in La_(0.85)Ca_(0.15)Mn_(1-x)Al_xO3 (x = 0.0 and 0.1) manganites. Al has been doped on its Mn site because it has no magnetic moment and its atomic radius is smaller than that of Mn. X-ray diffraction (XRD) pattern confirms the single phase character of both the samples with orthorhombic symmetry and space group Pnma. No structural change has been observed due to Al doping up to x = 0.1 except the decrease in lattice parameters. Dc conductivity data have been analyzed using different conduction mechanisms. Theoretical, models fitting show that the high temperature (T>Θ_D/2, Θ_D being the Debye temperature) dc conductivity (σ_(dc)) of these samples is due to adiabatic large polaron-hopping conduction. The value of polaron coupling constant, which is a measure of electron-phonon (e-ph) interaction, suggests the presence of strong e-ph interaction in x = 0.1 sample. It is observed that ferromagnetism (FM) decreases with Al doping. Minimum value of magnetization is obtained for x = 0.1 sample.