Cems Studies of Laser Treated Disordered Amorphous and Nanocrystalline Alloys
Conversion electrons provide information from a depth of about 150 nm for most iron rich alloys. Thus, surface effects can be effectively studied by means of Conversion Electron Mössbauer Spectroscopy (CEMS). Our study adopted this technique as the principal method for the investigation of surface modifications induced by pulsed excimer laser irradiation. The effects of laser beam on the magnetic microstructure of amorphous materials with Curie temperatures close-to-room temperature are presented. Such systems do not show the six-line Mössbauer patterns and represent an analytical challenge because the line-intensity ratios, which are correlated to magnetic texture, cannot be used as a measure of laser-induced modifications. In addition, we have chosen such materials, which after suitable temperature annealing exhibit nanocrystalline behavior. This enables the effects of laser treatment on both the amorphous and the nanocrystalline disordered structures to be investigated and discussed. Laser treatment performed under nitrogen and argon atmosphere affects the short-range order arrangement in a different manner. Through surface melting and subsequent rapid quenching, internal stresses are generated. The crystalline phase is eventually removed completely from the surface of nanocrystalline samples when exposed to laser fluence higher than 0.75 Jem-2.
KeywordsCrystallization Argon Calorimetry Retained
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