Influence of Calcium Substitution on Structural, Vibrational and Paramagnetic Properties of Magnesium Ferrite

The environment friendly calcium substituted magnesium ferrite with composition MgCa_xFe_2-xO₄ (x = 0.00, 0.01, 0.03, 0.05, 0.07) synthesized by the conventional solid – state reaction powdered samples are studied for structural, vibrational and spin characteristics for chemical sensor application. XRD patterns with Rietveld refinement reveal partial inverse spinel structure of the prepared samples with tentative cation occupancy. The rietveld refinement is performed to know the cation occupancy in the prepared samples which could be further helpful to exploit these ferrite materials for different technological applications. The intensity of ν Fe³⁺ -O stretching vibrational peaks arising from tetrahedral (ν 1 ) and octahedral (ν 2 ) sites in IR transmittance spectra are composition and cation distribution sensitive. The presence of Ca²⁺ /Mg²⁺ /Fe²⁺ ions is evidenced by the splitting of bands and shoulder peaks in IR transmittance spectra. The strong dipolar -dipolar interactions encourage broad asymmetric EPR derivative signal of Fe³⁺ ions. The substitution of diamagnetic Ca²⁺ dopant ions in lattice strengthens dipolar-dipolar interactions, broadens the resonance signal and higher g-values due to spin disorder (spin frustration).