The frequency dependence of the magnetic permeability as well as of the electrical impedance have been investigated for soft-magnetic granular FeHfO thin films. The impedance measurements indicate that capacitive effects resulting from the inhomogeneous structure of the layers are of no importance for the roll off of the permeability of the present films. The frequency behavior at various FeHfO thicknesses shows that eddy current effects start to play a role above thicknesses of 10 m. Below this thickness ferromagnetic resonance dominates the roll off.
We have studied the tunneling resistivity and magnetoresistance of reactive sputter deposited FeHfO and FeHfSiO thin granular films. Maximum magnetoresistance ratios at room temperature of 2% and 3.2% were observed for films with compositions of Fe 47 Hf 10 O 43 and Fe 40 Hf 6 Si 6 O 48 , respectively. The magnetoresistance shows a decrease with temperature, which cannot be explained by spin-dependent tunneling only. We propose that spin-flip scattering in the amorphous FeHf͑Si͒O matrix causes this decrease as function of temperature. A two current model for the tunnel magnetoresistance, taking into account spin-flip scattering, is presented which can describe the observed temperature dependence of the magnetoresistance.
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