Measurement of Magnetostriction in Single Crystals

A simplified procedure is given for determining the 5 magnetostriction constants of a single crystal of a ferromagnetic cubic crystal. The crystal is cut as a disk parallel to a (110) plane, and strain gauges are cemented to the surfaces to measure strains in [001] and [$1\overline{1}1$] directions. A magnetic field sufficient for saturation is oriented in 10° steps at various angles to the [001] direction, and magnetostriction is measured over a 90° range for each gauge. Each of the 18 data is then multiplied by suitable numbers, obtained by inversion of the strain matrix, to give the constants $h_1\cdots h_5$. The method is applied to a crystal of a 78 percent nickel-iron alloy to determine the magnetostriction associated with spontaneous magnetization in the [111] direction: ${\lambda }_{111}=\frac{2h_2}{3}+\frac{2h_5}{9}$, a quantity important in the "Permalloy problem." The constants are also determined for a single crystal of nickel.