Effect of rare earth ions (RE = La3+, Sm3+, Nd3+, and Gd3+) substitution on structural, magnetic properties, and dc electrical resistivity of Co0.5Ni0.5Fe2O4 ferrite

La 3+ , Sm 3+ , Nd 3+ , and Gd 3+ substituted Co–Ni system (Co 0.5 Ni 0.5 Fe 2– x RE x O 4 ; where RE 3+ = La 3+ , Sm 3+ , Nd 3+ , and Gd 3+ ; x = 0.0 and 0.06) ferrite materials have been synthesized using the solid-state reaction method. XRD, SEM, FTIR, DC electrical resistivity and VSM studies were carried out on these synthesized materials. It is found that RE 3+ ions have substituted Fe 3+ ions in the B sites. The X-ray powder diffraction pattern shows the formation of a spinel structure. No extra peak of rare earth ions was observed in the XRD pattern, possibly due to the small amount of doping of rare earth ions. The lattice parameter of the substituted ferrites is observed to increase as the ionic sizes of the RE ions increase, although fluctuations are sometimes observed. The samples are agglomerated and almost spherical, according to SEM analysis. The FTIR absorption bands represent the predicted range of spinel ferrites. D.C. electrical resistivity and saturation magnetization increase with the increase in substituted RE 3+ ions.