Effects of Nd-deficiency in Nd0.67Ba0.33MnO3 manganites on structural, magnetic and electrical transport properties

Abstract

In this work effect of Nd-deficient, Nd0.67-x⎕xBa0.33MnO3 (x = 0.05–0.23) compounds are synthesised via solid state reaction method. X-ray diffraction patterns confirm that all the compounds upto x = 0.1 are crystallised into a single phase orthorhombic crystal symmetry with Imma space group whereas some additional impurities such as Nd2Ba1Mn2O7 and Mn3O4 phases are witnessed for the x > 0.1 compositions. The obtained unit cell volume is found to increase with the increase of Nd-deficiency (x) due to the evolution of Mn2+ ions at the expense of Mn3+/Mn4+ ions as corroborated with the X-ray photoelectron spectra studies. Magnetic data suggest that the ferromagnetic (FM) to paramagnetic (PM) transition is found to decrease systematically with the increase of x, but without any measurable decrease in their magnetization values. Again, the low temperature magnetic ordering of Nd3+ ions below 25 K does not affect with the x. The magnetic properties are explained based on the multiple Double Exchange interactions. Electrical resistivity (ρ(T)) data indicates a clear metal–semiconductor transition (Tp) at 113 K and a maximum value of MR% is obtained at Tp for all compounds. ρ(T) is described with various theoretical models, with reasonable fits at the FM-metallic region, whereas the variable range hopping mechanism is well explained in the PM region.