Spatially resolved, in-situ measurements of the coercive force of thin film magnetic media

A method is presented for the nondestructive measurement of the coercive force of thin-film magnetic recording media. The technique involves the application of a precisely controlled erasing field to a previously written sequence of isolated magnetic transitions. Monitoring the playback response of the previously recorded pattern as a function of the erasing field permits an accurate estimate of the coercive force. The technique is applied in such a manner that coercive force variations along any radius can be measured