Articles you may be interested inAn induction method to calculate the complex permeability of soft magnetic films without a reference sample Rev. Sci. Instrum. 85, 054705 (2014); 10.1063/1.4876598 Improved accuracy thin film permeability extraction for a microstrip permeameter J. Appl. Phys. 113, 033906 (2013); 10.1063/1.4776715 Microwave permeability spectra of ferromagnetic thin films over a wide range of temperatures J. Appl. Phys. 93, 7202 (2003); 10.1063/1.1555902Broadband permeability measurement of ferromagnetic thin films or microwires by a coaxial line perturbation methodWe report a broad band technique allowing the measurement of the permeability of thin ferromagnetic films up to 6 GHz. The permeameter is based on a single coil technique. The input impedance of the loop is measured with and without the sample. The permeability is deduced from the impedance measurement using two approaches: the first one uses an equivalent electrical circuit model and the second a transmission line theory model. This leads to significant corrections compared to previous models. Calibration of the apparatus is presented using a known sample. Our two approaches are compared to the theoretical spectral permeability. The validity of the measurements is proven by showing a full spectral gyromagnetic response of a saturated magnetic sample at different fields.

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The dynamic properties of a 30-nm-thick permalloy film have been investigated through permeability measurements in the 100-MHz to 3-GHz range, in the presence of an external field applied along the easy axis. The permeability depends not only on the applied field, but also on the orientation of the field compared to the remnant magnetization of the sample. The application of an external field antiparallel to the magnetization may decrease the resonance frequency compared to the zero-field permeability. Ferromagnetic resonance equations provide a good description of the dynamic bistability at low fields, but do not account for the observed behavior in the whole bistability range. This is attributed to the occurrence of a nonuniform resonance.

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Free space permittivity measurements are presented on lattices of magnetic microwires. It is shown that the magnetic properties strongly affect the dielectric response of the composite. A model is presented, that accounts for these observations. The microwave dielectric function is shown to depend on the microwave impedance of the wire. Previous works on giant magneto impedance have provided a strong theoretical and experimental background, that may now be used to design composites with complex dielectric response, and also tuneable response. Some principles for making tuneable composites are presented, and illustrated by experimental results.

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Ferromagnetic materials are of great interest today for high frequency applications in microelectronics (M-RAMs, planar inductors, etc.) or magnetic recording systems, taking advantage of the high levels of saturation magnetization of ferromagnetics. We are presenting a setup permitting permeability measurements from 10 MHz up to 6 GHz in the 77–400 K temperature range. An existing single-coil perturbation technique is modified to allow precise and accurate microwave measurements. An experimental validation of the technique is performed. Measurements on a CoFeSiB thin film are presented. The clear effect of the temperature on the whole permeability spectra is shown for soft ferromagnetic thin films, including CoNbZr.