FORMATION OF UNIAXIAL MAGNETIC ANISOTROPY IN NICKEL BY PLASTIC DEFORMATION

Previous plastic elongation, or compression, of polycrystalline nickel was found to produce a uniaxial anisotropy. The easy axis of magnetization was parallel to the axis of previous elongation and at right angles to the axis of previous compression. The maximum value of the uniaxial anisotropy energy constant Ku was about 2700 erg/cm3 after 2.5% elongation. The observed anisotropy is shown to be due to a particular distribution of residual microstress, in which most of the volume of the specimen is in residual compression, balanced by a small volume in tension, after plastic elongation. These stresses, although balanced, introduce magnetoelastic effects which do not cancel in a nonsaturated specimen, and which thereby cause the observed anisotropy. Evidence for the assumed stress distribution was obtained by x-ray diffraction. © 1968 The American Institute of Physics.