Effect of the elastic modulus of the matrix on magnetostrictive strain in composites

The effect of the matrix material on the magnetostriction of composites con taining highly magnetostrictive particles has been studied. Experimental re sults showed that the elastic modulus of the matrix is an important factor determining the bulk magnetostriction of the composite. For a series of com posites with the same volume fraction of magnetostrictive particles but dif ferent matrix materials, the bulk magnetostriction was found to increase sy stematically with decreasing elastic modulus of the matrix. A model theory for the magnetostriction of such composites has been developed, based on tw o limiting assumptions: uniform strain or uniform stress inside the composi te. The theory was then used to predict the magnetostriction of the entire material from the volume fractions of the components, their elastic moduli and magnetostrictions. These predictions were in agreement with the experim ental results. It is concluded that to obtain a high magnetostriction and a dequate mechanical properties of a composite, the elastic moduli of the mag netostrictive phase and the matrix should be as close as possible in value. (C) 1999 American Institute of Physics. [S0003-6951(99)03106-X].