Parallel Line Type Permeameter for Thick Magnetic Material to Reduce the Error of Demagnetizing Field

We have developed a new high-frequency magnetic permeability evaluation method to suppress measurement errors due to demagnetizing fields of thick magnetic materials using parallel wires. The characteristic impedance of the parallel wires was designed to be around
$\mathbf{50}\ \mathbf{\Omega}$
. The magnetic field inside the sample has almost in-plane components, and even in thick samples, the perpendicular component of the magnetic field was canceled, and measurement errors due to demagnetizing fields were suppressed. The thick noise suppression sheet (Tokin, EFS-02, 0.5 mm in thickness) was evaluated, and the results almost corresponded to that of the standard method (Nicolson-Ross-Wier method). The ferromagnetic resonance frequency was around 3.5 GHz, almost corresponding to the intrinsic value. There was a clear resonance around 12 GHz, caused by the impedance mismatch or the cutoff frequency of the Transverse ElectroMagnetic (TEM) mode.