Permeability Measurements of Very Thin Magnetic Film Using a Flexible Microstrip-Line-Type Probe

Abstract

A highly sensitive probe to measure thin film permeability was developed based on the skin effect. A microstrip-line-type probe on a flexible polyimide substrate was fabricated and placed in contact with a magnetic thin film. The permeability was optimized by the Newton-Raphson method. The permeability of amorphous Co85Nb12Zr3 film (25 mm x 25 mm and 5 nm in thickness) was 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 7 GHz. The proposed method shows promise for the measurement of very thin film (less than 10 nm in thickness) because the contact surface between the flexible probe and thin film fits very well, resulting in improvement of the signal-to-noise ratio.