Doping-Induced Modifications in the Magnetoelectronic Properties in LaFeO3 Nanoparticles

Simultaneous effects of Na and Mn co-dopants on either site of LaFeO3 on the structural, magnetic, and low-temperature dielectric properties are studied in detail. The nanoparticles are prepared using a modified wet chemical route. The X-ray diffraction pattern is consistent with the formation of monophase with the distorted orthorhombic crystal structure. The average particle size is measured to be around 34 nm. The temperature and field dependent magnetization data reveals a drastic magnetic phase change of the modified co-doping system than LaFeO3 which is otherwise canted antiferromagnetic. This phase change is attributed to the mixed valence state of Mn ions present in the system due to substitutions. Several orders of change in the dielectric order parameter are found in the doped system. The low-temperature impedance spectra of the doped samples show dominant grain boundary relaxation as evidenced by modulus spectra. The conduction mechanism has been identified by calculating activation energies of relaxation from grain boundary and grain resistances as well as from ac conductivity analysis which are in good agreement. The typical calculated values are evidence of small polaronic hopping conduction mechanism in the sample.