EVOLUTION OF HIGH-FREQUENCY PERMEABILITY (UP TO 3GHZ) OF THIN FERROMAGNETIC COBALT-BASED LAYERS AS FUNCTION OF CONSTRAINT

We investigated the high frequency properties under tensile stress of various Co-based amorphous thin films deposited on thin mylar substrat es. The permeability of the layers was measured along the stress direc tion, in a frequency range that allowed the observation of the rotatio nal permeability and gyromagnetic resonance. The resonance linewidth i s hardly affected by the stress. A simple model assuming that the easy axis is constant over the whole film predicts the evolution of the in itial permeability and resonance frequency. This model is in good agre ement with measurements on CoZrMoNi, and yields an estimation of the m agnetostriction coefficient. In the case of CoNbZr, a poorer agreement is attributed to the local dispersion of magnetization direction.