Magnetic properties of the nanocrystalline bcc-Fe phase formed in FeZrBCu alloys investigated by using the radio-frequency collapse and sideband effects

An unconventional technique combining Mössbauer spectroscopy with the effects induced by magnetic radio-frequency (rf) fields (rf collapse and rf sidebands) is employed to study the microstructure and magnetic properties of nanocrystalline bcc-Fe phase formed by annealing amorphous Fe93−x−yZr7BxCuy alloys at 500–600 °C. The rf-Mössbauer experiments allow us to distinguish soft magnetic nanocrystals from magnetically harder microcrystalline phases. The complete rf collapse of the magnetic hyperfine structure occurs only in the amorphous and nanocrystalline phases and is suppressed by the formation of microcrystalline α-Fe. The rf sidebands disappear when the nanocrystalline phase is formed, what proves that magnetostriction vanishes. The rf-Mössbauer experiments performed as a function of the rf field intensity provide information regarding the distribution of anisotropy fields related to the size distribution of the bcc-Fe grains.