Microwave behavior in CoFe‐based single‐ and two‐phase magnetic microwires

Abstract

AbstractThe ferromagnetic resonance (FMR), spectra in the frequency range up to 12 GHz has been investigated as a function of applied DC magnetic field (up to 80 kA/m) for single‐phase CoFe‐based Pyrex‐coated microwire as well as for biphase microwires after depositing an outer shell, with hard (CoNi) and soft (FeNi) magnetic character, respectively. In addition, a parallel study on the low‐frequency magnetic hysteresis loop of all these samples has been performed. In particular, we have focused on the influence of the thickness of the insulating Pyrex layer and magnetic character of the outer magnetic phase. For single‐phase microwires, the increase of the Pyrex thickness results in a continuous strengthening of the circular magnetoelastic anisotropy of the CoFe‐based core as deduced from FMR and confirmed by low‐frequency measurements. For biphase microwires three absorption peaks are observed: two of them can be ascribed to each magnetic phase since FMR frequencies obey the Kittel condition for a thin film. A third absorption peak is observed at lower frequencies that does not follow such an equation and can be ascribed to a pure geometrical effect of these biphase microwires.