  We have investigated the microwave properties of epoxy-based composites
containing melt-extracted Co69.25Fe4. 25B13.5-xSi13Nbx (x=0, 1, 3) microwires
of various length annealed using a so-called combined current-modulation
annealing (CCMA) technique. The observation of a double-peak feature in the
permittivity spectra is believed due to the coexistence of the amorphous phase
and a small amount of nanocrystallites on the wires with a high Nb content.
CCMA was found to be favorable for a better-defined circular anisotropy of
microwires and had suppressed the highfrequency peak due to residual stress
relief for the composite with 25 mm long wires. Neither the shift of resonance
peak nor the characteristic double peak feature was detected for composites
containing as-cast 15 or 35 mm long microwires.
