Influence of Calcium Ions on the Structural and Magnetic Properties of Cd–Mg Ferrites Nanoparticles

Cadmium magnesium ferrites doped with calcium having the chemical formula Cd_0.5Mg_0.5–x Ca _x Fe₂O₄ (0.0≤ x ≤0.3) were prepared by the Co-precipitation method. X-ray diffraction analysis confirmed the formation of a single phase with spinel crystal structure for the samples. The lattice parameter is determined for each composition and has been found to increase from 8.505 Å to 8.626 Å with increasing calcium concentration. Cation distribution for the studied ferrite system is proposed in terms of the structural and magnetic properties by means of X-ray diffraction (XRD), infrared spectroscopy (IR), vibrating sample magnetometer (VSM) and is found to be reliable. The experimental and theoretical lattice constants show the same trend with increasing calcium concentration indicating the validity of the proposed cation distribution. The analysis of infrared spectra indicates the presence of splitting in the absorption band which may be attributed to the presence of small amounts of Fe²⁺ ions in the ferrite system. The appearance of a shoulder around 700 cm⁻¹ suggests the presence of calcium ions in the tetrahedral site. The addition of non magnetic calcium ions in the ferrites suppressed the A-interaction and developed a B–B interaction, which is reflected in reducing the saturation magnetization in the present samples. The coercive field (H_c ) is also found to increase by increasing of Ca²⁺ concentration and has been explained on the bases of direct relationship with anisotropy constant.