Fast and convenient technique for broadband measurements of the complex initial permeability of ferrimagnets

A new technique is proposed for the determination of spectra of the complex initial permeability of ferrimagnets at variable temperature over a broad frequency range. Different from the conventional techniques commonly used, the present method is based on a direct determination of the flux through the cross section of the sample. This is achieved by measuring the complex voltage induced in a pick-up coil, the reference voltage needed to drive the vector-voltmeter being taken at the right place, depending on the frequency range. Two measurement cells are used : a high frequency cell covering the range from 1 or 2 GHz down to 0.1 MHz and a low frequency cell below 0.1 MHz down to about 1 Hz. A technical description of the cells is given, mainly for the high frequency one which is the most sophisticated. Details are also provided on the calculation methods used for the permeability determination and examples of applications are shown. This technique is very suitable for automatization with a microcomputer.