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A highly sensitive and broadband method of obtaining thin film permeability without limitations in sample size was developed based on the high-frequency impedance change because of skin effect. A meander-type probe (3.5 mm × 2.5 mm, 2 turns) was placed in proximity of a (Co25Fe75)90B10 film (45 mm × 25 mm, 0.53 μm thick), and the permeability was optimized by Newton-Raphson method. The measured values are in good agreements with theoretical values based on the Landau-Lifshitz-Gilbert equation up to 10.6 GHz. The proposed method shows promise for measuring the permeability of wafer-sized samples in line because it is not restricted by size limitations.
Date of Publication: Oct. 2011