System for Measuring Thin-Film Permeability by Using a Parallel Line

A method of measuring the permeability of soft magnetic films at high frequencies was investigated. The main components of this system are a network analyzer and a parallel line. We attempted to discover why the value of the permeability given by the parallel line method is smaller than that given by the coil impedance method. We found that the leakage of field energy outside the line must be considered in evaluating the permeability correctly. The parameter a was introduced to describe the leakage of field energy. We then measured the value of the permeability by the parallel line method (10 MHz to 500 MHz), and the value obtained agreed well with measurements using a figure-8 type permeameter (1 MHz to 100 MHz). The parallel line was 15 mm long, 11.3 mm wide and 1.5 mm deep.