Experimental and modeling studies of the magnetomechanical effect in substituted cobalt ferrites for magnetoelastic stress sensors

This paper reports on experimental and modeling studies of the magnetomechanical effect in Mn- and Cr-substituted cobalt ferrites (CoMnxFe2-xO4 and CoCryFe2-yO4 with 0 <= x <= 0.3 and 0 <= y <= 0.4), which show promise for magnetoelastic sensor applications due to their high levels of magnetostriction lambda and strain derivative d lambda/dH. The difference in differential permeabilities measured along and perpendicular to uniaxial applied stresses was found to vary reversibly with applied stresses, indicating the feasibility of using the substituted cobalt ferrites for stress sensor applications. Stress-induced permeability changes were simulated using an extended magnetomechanical effect model which includes magnetocrystalline anisotropy K. The observed compositional dependence of stress sensitivity, which is related to lambda(s)/K, was reproduced in the simulations. This can be interpreted in terms of the effects of chemical substitution, which were found to increase magnetostriction but reduce the magnetocrystalline anisotropy within certain ranges of the substitute contents (near x=0.2 and y=0.4) and therefore accounts for the observed increase in stress sensitivities compared to pure cobalt ferrite. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3360582]