The magnetomechanical effect under torsional stress in a cobalt ferrite composite

Metal bonded cobalt ferrite composites are candidate materials for torque sensor applications because of their high magnetostriction lambda and particularly the high value of the derivative d lambda /dH. This paper reports on recent investigations of the magnetomechanical effect under torsional stress in (CoFe2O3)(0.98)(Ag0.97Ni0.03)(0.02). Magnetic and magnetomechanical properties were measured and the law of approach was used to model the effect of changing torsional stress on magnetization. In the model calculations an effective magnetic field due to the torsional stress was considered in order to calculate the anhysteretic magnetization. The change of amplitude and orientation of magnetization was determined by considering magnetoelastic, magnetostatic and anisotropic energies using a generalization of a model proposed by Garshelis. The measured and modeled results were in good agreement giving magnetomechanical sensitivities of 61 and 65 A/m per N(.)m, respectively.