Parallel line type permeameter for thick magnetic material to reduce the error of demagnetizing field

We have developed a new high-frequency permeability evaluation method to suppress measurement errors due to demagnetizing fields of thick magnetic materials sandwiched by parallel wires. The magnetic field inside the sample has almost in-plane components, and even in thick samples, the perpendicular component of the magnetic field was reduced, and measurement errors due to demagnetizing fields were suppressed. The characteristic impedance of the parallel wires was designed to be around 50 Ω. The permeability of the sample was optimized by the finite element analysis. The thick noise suppression sheet (NiZn ferrite sheet, 0.5 mm in thickness) was evaluated, and the results almost corresponded to that of the standard method (Nicolson-Ross-Weir method). The ferromagnetic resonance frequency was around 1.5 GHz, corresponding to the intrinsic value.