The temperature dependence of magnetostriction in a nickel crystal

This thesis describes an investigation of the longitudinal magnetostriction of a single crystal of nickel over the temperature range - 180ºC. to 360ºC. The most important measurement to be made at any temperature was of the saturation magnetostriction, but there is considerable interest in measuring the strain at different stages in the magnetization process, and this has been done at several temperatures. Measurements have been confined to two ellipsoidal specimens cut from the same crystal of nickel with their major axes along cube edge and cube diagonal crystallographic directions. Part 1 of the thesis describes the background to the work. The development of the theory of ferromagnetism is outlined, and the subject of magnetostriction introduced. Previous magnetostriction measurements, particularly on single crystals of nickel, are discussed. Part 2. ' surveys the apparatus used by previous workers for measuring magnetostriction over a range of temperatures, and discusses the design most suitable for the present investigation. Sections 2.3 to 2.7 describe in detail the apparatus used for the high temperature measurements, and section 2.10 the modifications which were necessary for use below room temperature. The preparation of the specimens from the single crystal is described in section 2.8. In Part 3 the results are presented, and their significance is discussed in relation to theories of the magnetization process.