Magnetic and Magnetoelastic Properties of Ni-Substituted Cobalt Ferrite

In this letter, magnetic and magnetostriction studies were performed on spinel ferrite Co _{1– x} Ni _x Fe ₂ O ₄ (CNF series) with $0.0 < x < 0.5$ . All the samples were synthesized by the conventional ceramic method and confirmed to be forming pure spinel phase. The unit cell parameter showed gradual decrease with increasing Ni content. A linear decrease in saturation magnetization $(M_s)$ and coercivity $(H_c)$ was observed with increasing Ni substitution, which could be attributed to reduced magneto-crystalline anisotropy. The room temperature magnetostriction studies revealed a slow decrease in maximum magnetostriction, and interestingly, for 20% reduction of cobalt concentration, i.e., for $x$ = 0.2, a magnetostrictive strain of −164 ppm and substantially high stress sensitivity of −56 × 10 ⁻⁶ A ⁻¹ m were observed, making Co _0.8 Ni _0.2 Fe ₂ O ₄ suitable for application as a magnetostrictive stress-sensing material.