Permeability Measurements of Magnetic Thin Film with Microstrip Probe

Abstract

A highly sensitive and broadband method of obtaining thin f lm permeability without sample-size limitations was developed based on the change in high-frequency impedance due to the skin effect. A microstrip probe with impedance matching of 50 Ω was fabricated, and placed in proximity to a magnetic thin film. The permeability was optimized with the Newton-Raphson method. The permeability of CoFeB f lm (45 mm  25 mm and 0.5 m in thickness) and that of FeCoB/Ru film (50 mm  40 mm and 0.2 m in thickness) were evaluated using a permeameter. The measured values were in rough agreement with theoretical values based on the Landau-Lifshitz-Gilbert equation and eddy current generation up to 30 GHz. The proposed method offers promise for measuring the permeability of wafer-sized samples in line because it is not restricted by size limitations.