From dipolar interactions of a random distribution of ferromagnetic particles to magnetostriction

The magnetostriction of a soft matrix, nonmagnetic, randomly filled by ferromagnetic particles is measured and calculated. Dipolar forces between particles have been calculated using a simple model of particles with the same permanent magnetic moment. Forces are injected in an FEM software to evaluate the strain of the composite. The longitudinal strain calculated for a cylinder-shape distribution is positive. A sample with the same shape has been prepared and shows the same strain.