Structural, magnetic, and dielectric properties of solution combustion synthesized LaFeO, LaFeMnO, and LaMnO perovskites.

Nanocrystalline LaFeO, LaFeMnO, and LaMnO perovskites have been synthesized by a novel solution combustion route, in which oxalyl dihydrazide (ODH) has been used as a fuel. These materials have been characterized using several physicochemical techniques. LaFeO and LaFeMnO adopt an orthorhombic structure and LaMnO crystallizes in a rhombohedral structure as demonstrated by X-ray diffraction (XRD) patterns. The microporous character of the materials due to huge gas evolution during preparation has been revealed by field emission scanning electron microscopy (FESEM) images. Corresponding elements are present in stoichiometric amounts in all perovskites as revealed by energy dispersive X-ray spectroscopy (EDXS) analyses. X-ray photoelectron spectroscopy (XPS) studies demonstrate the presence of La, Fe, Fe, Mn, and Mn species in the respective materials. Absorption bands in the frequency range of 500-600 cm related to Fe-O/Mn-O bonds in FeO/MnO octahedra are observed in Fourier transform infrared (FTIR) spectra. Raman spectroscopy depicts symmetric modes related to metal-oxygen bonds in orthorhombic and rhombohedral structures. Weak ferromagnetism has been observed in LaFeO and LaFeMnO which is due to superexchange interaction between the magnetic cations. However, LaMnO shows paramagnetic behavior. The electrical characteristics exhibit the lowest dielectric loss for magnetic LaFeO among the LaFeO, LaFeMnO, and LaMnO perovskites studied here.