Impact of lanthanum on structural, optical, dielectric and magnetic properties of Mn1-x,Cu,Fe1.85La0.1504 spinel nanoferrites

Spinel Mn(1-x)CuxFe(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 La3+ 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.