Glycine-nitrate auto-combustion synthesis and magnetic properties of nanocrystalline NdAlxFe1–xO3 perovskites

Abstract

The effect of substitution of Fe3+ by Al3+ on the structure and magnetic properties of NdAlxFe1–xO3 perovskite nano-powders (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5) prepared by the glycine-nitrate auto-combustion method was studied. All samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and energy dispersive X-ray spectroscopy (EDX). The magnetic properties of the samples were investigated using a vibrating sample magnetometer (VSM). The X-ray results for all samples reveal the formation of an orthorhombic perovskite phase (space group Pbnm) with no secondary phase. The crystallite sizes of the nanoparticles are found to decrease with increasing Al content, and are in the range of 53–38 nm. SEM images show spherical nanoparticles with agglomeration. The FT-IR spectra confirm the presence of metal oxygen bonds. The M–H loop of the pristine NdFeO3 sample is antiferromagnetic in the a/b plane with weak ferromagnetism in the c-axis. Introducing Al inclusions in the pristine polycrystal thereby creating magnetic vacancies is seen to influence the magnetic properties. The magnetic dilution results in enhanced magnetisation at low Al content; x = 0.1, 0.2 (saturation magnetisation being 2.08 and 2.05 emu/g, respectively) compared to the pristine sample with a saturation magnetisation of 1.43 emu/g due to increased exchange interaction. Also dilution with nonmagnetic dopant induces the phase transition from weak ferromagnetic to paramagnetic depending on the impurity concentration. The coercive field for NdFeO3 is found to be equal to 1950 Oe and decreases with Al-substitution. These findings lay a ground work for research in tuning magnetic properties and in spintronics with potential applications in data storage, switches and electronic devices.