New technique to measure low-frequency permeability of thin magnetic films surrounded by a current sheet in a multilayer environment

A new technique of inductive measurement to determine the initial magnetic permeability mu(r) of Yttrium Iron Garnet (YIG) thin films has been conceived and developed. The magnetic material is deposited by radio-frequency sputtering between two copper thin layers on alumina substrate. After different tests considering the geometrical, morphological and magnetic properties, we have established a protocol permitting to manufacture a prototype in an original design. The performance of the fabricated micro-inductor has been checked using the Kerr effect, X-ray diffraction and scanning electron microscopy. To obtain accurate measurement of mu(r), we have used a four- point probe test bench and a precision LCR meter. This technique was first validated on a larger scale by finding mu(r) = 1 for the dielectric layers. Then, the current sheet method was validated with thick layers of commercial YIG. From several tests the magnetic permeability of YIG thin films has been evaluated as 25.