Shape effect in the magnetostriction of ferromagnetic composite

The magnetostriction of composite consisting of a soft matrix, non-magnetic, randomly filled by ferromagnetic particles is measured. The measured elongation on cylinder-shaped samples displays shape dependence. A model based on the demagnetizing field and the effective Young’s modulus is provided. Both calculation and measurement show a positive magnetostriction with larger values as the samples are flatter. The model is derived to have the behavior of the elongation as a function of the filling factor. An expression of the optimal filling factor, providing a maximal strain, is also expressed.