The high-frequency susceptibility spectra of ferromagnetic films supporting a weak-stripe-domain structure are computed using a 2D dynamic micromagnetic model that we have developed. The existence of multiple resonances resulting from the excitation of surface and volume modes is predicted. The main features of spectra (number of resonances, resonance frequencies, intensities, and linewidths) strongly depend on the equilibrium spin configuration and on the rf exciting field orientation. These theoretical results are successfully compared with zero-field microwave permeability measurements.

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.

A new method to measure the microwave permeability of ferromagnetic thin film or microwires from 50 MHz up to 18 GHz is presented. In contrast with all previous permeameters based on perturbation techniques, our permeameter does not require any reference sample for calibration, which is a definite advantage, as it is very difficult to have a reference magnetic sample of known permeability. In our technique, a network analyzer detects the small perturbation of the impedance of a coaxial line cell loaded by the magnetic sample. Satisfactory sensitivity is achieved, even for magnetic volume fraction as low as 10−4. To assess the validity of this new technique, comparisons are performed with three other methods on different samples, in particular on ferromagnetic wires. It is shown that in the case of very soft magnetic materials, the shape of the sample affects the permeability measured with a conventional permeameter.