RELATION BETWEEN FREQUENCY PERMEABILITY AND STRUCTURAL-PROPERTIES OF CO-FE-SI-B ALLOYS DEPOSITED BY ION-BEAM SPUTTERING

In the present study, structural properties and microwave permeability of (Co88Fe9Si3)100-xBx (5 less-than-or-equal-to x less-than-or-equal-to 15 at.%) films prepared by ion beam sputtering (IBS) were investigated as a function of film composition and deposition parameters. A microcrystalline phase with <111> orientation normal to the film plane is obtained for low boron content (x < 6at.%) and deposition rate above 2 nm/min, whereas the material is amorphous or partially crystallized at 1,5 nm/min or for a boron content of 12 at.%. In-plane uniaxial anisotropy field H(k) and coercive force H(c) have also been found to be strongly dependent on deposition rate. For microcrystalline films prepared at high growth rate, permeability measurements in the gigahertz range show that gyromagnetic resonance frequency is 1.5 GHz whereas the real part of relative permeability mu' is 1100 along the hard axis and 1 along the easy axis. In contrast amorphous films deposited at low deposition rate exhibit semihard properties. The complex permeability spectra shows a low rotational permeability mu'(< 200) combined with a high resonance frequency more than 3 Ghz. This behavior might be attributed to the structural inhomogeneities in alloy.