Comparison between different methods for evaluating the anisotropy field distribution in recording systems

The determination of the anisotropy field distribution P(Ha) is made by the second derivative of the magnetization measured perpendicularly to the easy magnetization direction, in the range from saturation to remanence, for a number of magnetic recording systems. The transverse susceptibility X(H) is measured in the same systems. For the systems where the particles are "perfectly" aligned the peak of P(Ha) is located at the same field of the peak of X(H). In the systems where an appreciable fraction of particles are misaligned the peak of P(Ha) is shifted to lower fields while that of X(H) does not change its position. The coincidence of the two peaks is assumed as a criterion for the validity of the P(Ha) distribution.