High frequency magnetic behavior through the magnetoimpedance effect in CoFeB/(Ta, Ag, Cu) multilayered ferromagnetic thin films

摘要

We studied the dynamics of magnetization through an investigation of themagnetoimpedance effect in CoFeB/(Ta, Ag, Cu) multilayered thin films grown bymagnetron sputtering. Impedance measurements were analyzed in terms of themechanisms responsible for their variations at different frequency intervalsand the magnetic and structural properties of the multilayers. Analysis of themechanisms responsible for magnetoimpedance according to frequency and externalmagnetic field showed that for the CoFeB/Cu multilayer, ferromagnetic resonance(FMR) contributes significantly to the magnetoimpedance effect at frequenciesclose to 470 MHz. This frequency is low when compared to the results obtainedfor CoFeB/Ta and CoFeB/Ag multilayers and is a result of the anisotropydistribution and non-formation of regular bilayers in this sample. The MImaxvalues occurred at different frequencies according to the used non-magneticmetal. Variations between 25% and 30% were seen for a localized frequency band,as in the case of CoFeB/Ta and CoFeB/Ag, as well as for a wide frequency range,in the case of CoFeB/Cu.