Magnetic and magnetoelastic properties of Ga-substituted cobalt ferrite

Magnetic and magnetoelastic properties of a series of Ga-substituted cobalt ferrites, CoGaxFe2−xO4 (x=0.0–0.8), have been investigated. The Curie temperature TC and hysteresis properties were found to vary with gallium content (x), which indicates that exchange and anisotropy energies changed as a result of substitution of Ga for Fe. The maximum magnitude of magnetostriction decreased monotonically with increasing gallium content over the range x=0.0–0.8. The rate of change of magnetostriction with applied magnetic field (dλ∕dH) showed a maximum value of 3.2×10−9A−1m for x=0.2. This is the highest value among recently reported cobalt ferrite based materials. It was found that the dependence of magnetic and magnetoelastic properties on the amount of substituent (x) was different for Mn, Cr, and Ga. This is considered to be due to the differences in cation site occupancy preferences of the elements within the spinel crystal structure: Mn3+ and Cr3+ prefer the octahedral (B) sites, whereas Ga3+ prefers the t...