About cookies on this site Our websites require some cookies to function properly (required). In addition, other cookies may be used with your consent to analyze site usage, improve the user experience and for advertising. For more information, please review your options. By visiting our website, you agree to our processing of information as described in IBM’sprivacy statement. To provide a smooth navigation, your cookie preferences will be shared across the IBM web domains listed here.
Publication
IEEE Transactions on Magnetics
Paper
The High Field, High Frequency Permeability of Narrow, Thin-Film Magnetic Stripes
Abstract
We have constructed a high-frequency permeameter to measure the magnetic response of magnetic thin-film stripes to sinusoidally oscillating rf magnetic fields of up to 5 Oe over the frequency range from 300 kHz to 30 MHz. These Fields simulate those used to drive magnetic heads allowing the magnetic dynamics during recording of the magnetic thin-films in a recording head to be studied in a much simpler geometry. Measurements were performed on single and multi-layer permalloy thin-films, photo lithographic ally patterned into arrays of 3 pm to 1000 pm wide rectangles, 1 cm long. The low field-amplitude permeability of narrow unlaminated permalloy stripes is frequency independent except for eddy current losses as expected for magnetization rotation. At higher fields the magnetic response increases at frequencies below 10 MHz with increasing drive amplitude as domain wall motion becomes significant (as is seen in heads). Our results are consistent w ith the expected domain wall mobility (around 2 × 10<sup>3</sup>cm/(s-Oe) for 2 pm thick films). At still higher fields the permeability drops as the film saturates above H<inf>k</inf>. Because of the high density of walls in microscopic structures, wall motion is the dominant flux conduction mechanism below 30 MHz at high drive fields. This means that wall oscillations (seen in dynamic-Kerr images of recording heads) determine the head response below 30 MHz during writing. © 1991 IEEE