Magnetic Properties of Spinel Cobalt–Manganese Ferrites

Cobalt ferrite (CoFe₂O₄) and manganese substituted cobalt ferrite (Co_0.25Mn_0.75Fe₂O₄) were synthesized by coprecipitation and sol-gel methods. X-ray diffraction revealed that manganese ions slightly enlarged the crystal lattice with respect to pure cobalt ferrite. Magnetization, linear magnetostriction, and piezomagnetic coefficient values tended to decrease with the ion substitution. Linear magnetostriction dropped from a value of -111.5 ppm for cobalt ferrite to values of -22.6 and -30.6 ppm for the substituted samples obtained from coprecipitation and sol-gel, respectively. The sample prepared by sol-gel technique resulted in a higher magnetization, magnetostriction, and piezomagnetic coefficient than that synthesized by coprecipitation method.