ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
A new low-field resonance technique for determining the initial hard-axis permeability (μ') of materials used in thin film and magnetoresistive heads has been developed. The initial μ' is found to be less than 4πM/Hk due to the internal effective magnetostatic field caused by magnetization ripple, in agreement with the theory and transverse biased initial susceptibility measurements of Hoffmann and others.1 A proper consideration of the in-plane susceptibility for real films includes the Stoner–Wohlfarth anisotropy field (Hk)−1 dependence, modified by the factors due to ripple (B) and skew (E) as defined by Hoffmann. The latter produce internal fields that shift the Kittel resonance versus field plots (fr2 vs H) leftward from their ideal symmetric positions for angles of 0° and 90° between bias field and preferred axis. When resonance data from both orientations are computer-fit simultaneously, we determine the parameters B and E as well as Hk and Ms. The coefficients are believed to have more consistency than those obtained using Hk found from hard-axis magnetization curves. The reduction of the hard-axis μ' is by the factor (1+B+E)−1. The high frequency properties (300 kHz–3 GHz) were measured using a test jig consisting of a shorted-shield strip-line section with a one-turn inductively coupled loop containing the sample and located at the shorted end. Bias fields from zero to 100 Oe were employed. We measure fR reproducibly with an uncertainty of less than 1%. This analysis determines the parameters of interest from measurements under dynamic conditions. Results include Permalloy and amorphous TM-metalloid films. When annealed to reduce Hk, their B parameters increase in accord with theory, assuming invariant structure constants, S. Beyond head applications, the method relates to thin film microwave devices operating near fr in zero field.2
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.354066
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