Temperature Dependence of Magnetostriction of Co₁₊ₓ Geₓ Fe₂₋₂ₓ O₄ for Magnetostrictive Sensor and Actuator Applications

The temperature dependence of the magnetoelastic properties of a series of germanium/cobalt co-substituted cobalt ferrite samples has been measured. Magnetostriction loops of the compositions Co1+xGexFe2-2xO4(x = 0.1 , 0.3, and 0.6) were measured over a temperature range of 250-400 K. Germanium/cobalt co-substitution was found to change the Curie temperature, anisotropy, and the magnetostriction coefficients in the crystal directions of [100] and [111]. Both magnetostriction and strain sensitivity were seen to decrease in magnitude with increasing temperature. Co1.1Ge0.1Fe1.8O4was found to have a maximum sensitivity (dlambda/dH)sigmaof 2.6 times 10-9A-1.m, which is twice the value obtained for pure cobalt ferrite, without any decrease in maximum magnetostriction in the linear region.