Clemens Schmutz

Integration of crossed anisotropy magnetic core into toroidal thin-film inductors

A new approach to RF thin-film inductors with an integrated magnetic core has been investigated. A toroidal inductor design was realized in thin-film technology aiming at small-signal applications in the frequency range from 10 MHz to 1 GHz. The magnetic core consists of a multilayer of sputter deposited soft magnetic FeCoBSi. The individual magnetic films were deposited in a way to realize a crossed magnetic anisotropy in the core. High-frequency measurements of the multilayers already illustrated the advantages of the unique magnetic geometry. The influence and benefit of such a magnetic core on the toroid microinductor is discussed. The results show that such crossed anisotropy microinductors are a very promising alternative to common planar spiral inductors in the RF range.

Permeability and Magnetic Properties of Ferromagnetic NiFe/FeCoBSi Bilayers for High-Frequency Applications

In order to adjust the ferromagnetic resonance (FMR) frequency of thin NiFe films, ferromagnetic polycrystalline/amorphous NiFe/FeCoBSi bilayers using radio frequency magnetron sputtering were produced. Herein, the higher anisotropy field Hk of a ferromagnetic FeCoBSi was used to shift the FMR-frequency of the bilayer. Static and dynamic magnetic properties of the films were investigated by quasi-static magnetometry and by high frequency permeability measurements, respectively. The dynamic anisotropy field Hkdyn calculated from the FMR frequency of a single 100-nm NiFe-layer is shifted from mu0Hkdyn=0.5 mT to mu0Hkdyn=2.8 mT in a FeCoBSi(80 nm)/NiFe(20 nm) bilayer; whereas, the FMR frequency is congruently enhanced from 0.9 to 2.0 GHz. The permeability decreased from mu=2000 to mu=500. A linear dependence for the adjustment of the relevant magnetic parameters with NiFe:FeCoBSi ratio is demonstrated, opening the possibility to individually tailor magnetic properties of magnetic films for high-frequency applications