New optical technique for bulk magnetostriction measurement

A new optical technique was applied to the measurement of magnetostriction in bulk samples. This technique utilizes an optical fiber bundle, AC-modula ted light and lock-in detection. Deformation of the sample is determined fr om the ratio of the incident and reflected light intensities. Noise due to the instability of the light source is eliminated by obtaining the ratio of the incident and reflected light intensities, and the noise caused in the detector circuit can be reduced by lock-in detection. The performance of th is method was characterized with a series of measurements using a gold film and crystal disks of pure iron and nickel. This technique offers a resolut ion of 0.5 nm and is sensitive enough to measure magnetostriction as small as 5 x 10(-7) in 1 mm thick samples. (C) 2000 Elsevier Science B.V. All rig hts reserved.