Measurement of the variation of Young modulus on internal stress in ferromagnetics by speckle interferometry

A heterodyne speckle interferometric system is employed to measure the dependence of E (Young modulus) on stress in a magnetic sample. That elastic modulus is obtained by mean of the first natural frequency of a cylindrical bar placed in a solenoid for both, saturated and demagnetized states. The experimental non-contact set-up allows to carry out the measurements of the vibration of the material in a wide bandwidth with a high precission. The method has general validity. However, different samples of nickel are used, being the results in agreement with the theoretical calculus.