Temperature hysteresis and relaxation effects in amorphous Fe-Ni-Zr alloys (abstract)

Amorphous Fe-Ni-Zr alloys in the ‘‘as quenched’’ and irradiated state have been studied with 57Fe Mössbauer spectroscopy and ac and dc susceptibility. Samples were irradiated by 14-MeV neutrons at room temperature to fluences of ≊1017 ns/cm2 corresponding to a dpa of 3×10−4 at the Lawrence Livermore National Laboratory RTNS-II facility. Two samples (Fe89.7Ni0.3Zr10 and Fe70Ni20Zr10) ‘‘as quenched’’ and irradiated, have been studied between room temperature and ≊4 K. ac susceptibility shows reentrant magnetic behavior for both alloys. Temperature hysteresis (no applied fields) is observed initially in the Mössbauer spectra for both alloys, ‘‘as quenched’’ and irradiated. It decreases and virtually disappears after a few thermal cycles between 20 K and room temperature. Relaxation effects are present in the magnetic hyperfine spectra of both alloys, ‘‘as quenched’’ and irradiated. The usually assumed proportionality between the magnetic hyperfine splitting and the magnetization is probably not valid for these alloys.