Effect of Co concentration on cation distribution and magnetic and magneto-optical properties of Co_xZn_1-xFe₂O₄ nanoparticles synthesized with citrate precursor method

Magnetic properties of mixed spinel ferrites are determined, in great extent, by the magnetic cation distribution among tetrahedral and octahedral positions in a crystal. In the case of CoZn-ferrites, most researchers reported a predominant localization of the divalent cobalt ions in octahedral positions. Using the citrate precursor auto-combustion method, we successfully synthesized Co_xZn_1-xFe₂O₄ nanoparticles (x changed from 0.0 to 0.5) with an approximately evenly distribution of Co²⁺ ions between these interstitial positions. Fe³⁺ ions are localized preferably in octahedral positions. This type of 3d-ion distribution predetermined the combination of the large saturation magnetization and very low coercive field of the nanoparticles, which may be of importance for applications. MCD spectra of Co_xZn_1-xFe₂O₄ nanoparticles are studied here for the first time. Revealed intense MCD peak at 1.75 eV corresponds to the emission wavelength (710 nm) of some lasers, e.g., ALP-710 nm (NKT Photonics, Denmark) which may be of interest for photonic devices.