We present the first direct evidence of structural anisotropy due to anelastic polarization produced by mechanical creep, in the form of the anisotropic diffraction intensities observed by energy dispersive x-ray diffraction method. We suggest that this structural anisotropy is the origin of the creep-induced magnetic anisotropy.

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The frequency dependence of t.he transverse biased permeability ,u: if ) has been measured up to 250 MHz in thin (0.044 pm) and thick (2.1 pm) unpatterned sputtered permalloy films with uniaxial anisotropy. In these films, the initial permeability along the hard axis can be described by the classical eddy current damping model assuming uniform rotation. For both films, pi at low frequency agrees reasonably well with Hoffman's ripple model assuming appropriate values for the structure factor. In the thin film, pi (f ) is independent of frequency within experimentai error up to at least 250 MHz. However, in the thick film pi(f ) decreases more rapidly with frequency than can be explained by classical eddy currents, when the transverse bias field HB is not very large compared to the net anisotropy field. The value of H, at which &(f ) reaches a maximum amplitude is also found to increase monotonically with increasing frequency, also inconsistent wit.h simple eddy c.urrent predictions, It is suggested that the formation of ripple walls leads to anomalous eddy current losses similar to that observed in bulk materials.

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Absrract-A technlque Is described for using a Magnetic Force Microscope (MFM) as a local fleld source for mapplng the sensltivlty function of magnetic recordlng heads. The resultsobtained from applying this technique to both magneto-resistlve and lnductlve recording heads are discussed.