The influence of Ca substitution on LaFeO 3 nanoparticles in terms of structural and magnetic properties.

BACKGROUND: The nanocrystalline structure of La1 -x Ca x FeO3 was prepared by a sol-gel method involving an auto-combustion process. The incorporation of rare-earths in LaFeO3 induces strain in magnetic properties, especially in terms of the following parameters: replacement amount, oxygen partial pressure, and calcination temperature.

METHODS: To determine the effects of the amount of Ca2+ ion doping agent and the calcination temperature on the microstructure, particle morphology, and magnetic properties of LaFeO3 crystal, we performed the following respective analytical methods: X-ray powder diffraction, Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy, and vibrating sample magnetometer tests.

RESULTS: The orthorhombic structure of LaFeO3 perovskite did not change even when it was doped with Ca2+ ions, and its space group continued to be Pnma (No.62). FT-IR spectra confirmed that the main band appearing at 568 cm-1 is due to the antisymmetric stretching vibration of Fe-O-Fe bonds in FeO6 . The introduction of Ca inhibits the growth of grains but the morphology of particles is improved. With an increasing concentration of Ca2+ ions, magnetic behavior of the samples also witnessed an increasing trend in a proportionate manner. With an increase in calcination temperature, the enclosed area of the magnetic hysteresis curve of the sample reduced remarkably.

CONCLUSIONS: The growth of nanoparticles can be restrained with an increase of Ca content that is used as doping agent. The magnetic behavior of La1 -x Ca x FeO3 tilts towards G-type antiferromagnetism; the magnetic orientation is achieved from the super exchange interaction of Fe3+ ions with oxygen ions.