Measurement of field-dependence elastic modulus and magnetomechanical coupling factor by optical heterodyne interferometry

Optical heterodyne interferometry is applied to determine the change in ela stic modulus (Delta E) with the applied magnetic field and the magnetoelast ic coupling coefficient k. The samples used are thin nickel rods and wires up to 1 mm in diameter positioned within the magnetic field of a solenoid. The Young's modulus is determined from the first natural vibration frequenc y. A dual methodology is evaluated, respectively, involving free and forced sample vibrations. Estimations are also made of eddy current-induced magne tic losses of the material. This technique permits point-like detection, in volving an illuminated zone approximately 20 mu m in diameter, without cont act with the sample. (C) 1999 Elsevier Science B.V. All rights reserved.