The Measurement of Magnetostriction by means of Strain Gauge

For the purpose of studying the relation of magnetostriction to technical magnetization, we used a strain gauge to measure the magnetostriction of long rod single crystals of 3.2% Si-Steel, and compared the results with those which had formerly been obtained on the same samples by using a mechano-optical lever. The latter method was applied in measuring the overall elongation of a rod sample, while the strain gauge recorded the local magnetostriction. In some of the samples, these two methods often gave remarkable difference in the results. This is mainly due to the fact that the sample is not uniformly magnetized, especially in lower magnetic field; the magnetostriction measured by the optical lever method showed only the mean change of length even if the magnetization is not uniform, while the result obtained by the strain gauge corresponds rather well to the local magnetization. The latter method is, therefore, more appropriate for relating the magnetostriction to the magnetization. We also determined the magnetostriction constants which are slightly different from the previous results.