Impact of lanthanum on structural, optical, dielectric and magnetic properties of Mn1-Cu Fe1.85La0.15O4 spinel nanoferrites

Abstract Spinel Mn 1- x Cu x Fe 1.85 La 0.15 O 4 ( x = 0.2, 0.4, 0.6, 0.8 and 1) nanoferrites were synthesised by means of the sonochemical method. The effect of La 3+ on the structural, optical, dielectric and magnetic properties of Cu–Mn nanoferrites was investigated through various characterisation techniques. X-ray diffraction results showed the prepared nanoferrites to have a face‒centred cubic spinel structure and an average crystal size of 26–58 nm. The Fourier transform infrared spectra showed the presence of two absorption bands related to tetrahedral (537, 588 and 700 cm −1 ) and octahedral (450 cm −1 ) group complexes within the spinel ferrite lattice system. X-ray photoelectron spectroscopy confirmed the elements and oxidation states of Cu 2p, La 3d, Fe 2p, Mn 2p and O 1 s elements. The surface morphology of the nanoferrites revealed a spherical shape and the elements of the prepared nanoferrites uniformly arose with the designed chemical formula, which was confirmed by scanning electron microscopy-energy dispersive X-ray spectroscopy. The optical bandgap energy values (5.23–5.42 eV) of the nanoferrites were examined from the observed wavelength (228–237 nm) of ultraviolet diffuse reflectance spectroscopy. The dielectric measurements were acquired over a wide range of frequencies (1 kHz to 5 MHz) and showed a low dielectric constant and dielectric loss. The magnetic properties could be determined with a vibrating sample magnetometer, which revealed that these nanoferrites were made up of soft magnetic material and had a ferromagnetic nature.