Investigation of the Structure of Ferromagnetic Films by Means of the Differential Susceptibility

The differential susceptibility of thin polycrystalline iron–nickel‐films has been measured. From the results the structure constant, S , could be determined. The experiments gave the same field dependence for the susceptibility as was expected by former calculations. The values for S , evaluated from the experiment, can be explained quantitatively by the mean crystallite diameter, the magnetocrystalline anisotropy, the magnetostriction constants, and the intrinsic stresses, if one uses the Doyle‐Finnegan formula for the calculation. The measurements show quantitatively the existence of the intrinsic demagnetizing field, which has been predicted by micromagnetic calculations and which contributes to the whole effective field.