Anisotropy correlation function and grain-size distribution in polycrystalline magnetic materials

It is shown how the anisotropy correlation function, which largely determines linewidth and magnetic loss in poly-crystals, can be inferred from an analysis of micrograph pictures which show the grain boundaries at a polished surface. The second derivative of the correlation function is shown to be proportional to the cord-length distribution. At high-wave numbers the spectrum of the random anisotropy field is found to be inversely proportional to the fourth power of the wave number and the first power of the mean cord length. The relation between cord-length distribution and grain-diameter distribution is discussed.