Interaction of Alpha Particle Beams with Fe-Based and FeNi-Based Glassy Ferromagnets
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ABSTRACT Samples of Fe78B,3Si9 and Fe 40Ni 38MonB48 metallic glasses were irradiated with alpha particle beams (W=2.8 MeV) using radiation doses of 1016 and 107 cm-2. Irradiation-induced effects on the magnetic texture and phase composition of alloy samples were studied by Mossbauer spectroscopy. Related morphological changes and resultant crystalline precipitates were characterized by scanning electron microscopy. The evolution of phases and microstructure during the radiation-induced amorphous-to-crystalline transformation was found ,:o depend on the particle flux and sample composition. The lowest radiation dose employed was found to be more effective in inducing amorphous-to-crystalline transformations in both ferromagnetic alloys studied. In addition, the FeNi-based amorphous system investigated was found to be more stable than the Fe-based metallic glass, exposed to the same particle-beam irradiation conditions. By stimulating unconventional pathways for the crystallization process, the interaction of alpha particle beams with glassy ferromagnets offers unique opportunities to understand the fundamentals of nucleation and growth in amorphous magnets.
INTRODUCTION In order to understand the relationship between magnetic parameters and structural characteristics of alloy phases, a particularly intriguing approach involves the study of phase evolution and microstructure development during various laser and particle beam irradiation treatments.' In the present work we report new investigations on the fundamentals of ionsolid interactions, by considering alpha-particle-beam effects on the magnetic and structural properties of Fe-based and FeNi-based glassy ferromagnets. Due to its local-probe character, MOssbauer spectroscopy was used to monitor the changes in magnetic anisotropy and phase composition. Related morphological modifications and the formation of crystalline precipitates in the Fe75B 3Si 9 and Fe 40Ni 38Mo 4 Bl 8 metallic glasses were examined by scanning electron microscopy (SEM). Irradiation-driven property changes were studied as a function of alpha particle flux and composition of the ferromagnetic alloy systems. EXPERIMENTAL Amorphous alloys Fe78B,3Si 9 (Metglas 2605 TCA) and Fe40Ni 38Mo 4Bl8 (Metglas 2826 MB) were supplied by Allied Signal Inc. in the form of 20 pm thick ribbons. The magnetostriction constants had the values 27 and 12 ppm, respectively. Square samples (2x2 cm) were cut from the foils and exposed to radiation doses of 1016 and l0ol cm-2, generated by the 2.8 MeV alpha particle beam at the Institute of Atomic Physics Bucharest cyclotron facility. Room-temperature transmission Mbssbauer spectra were recorded with the y rays perpendicular to the ribbon plane using a constant acceleration spectrometer (Ranger Scientific). The 25-mCi 7 ray source was 57Co diffused in a Rh matrix. Least-squares fitting of the M6ssbauer spectra corresponding to the amorphous and irradiated samples was performed with the NORMOS program. 5 The relative areas of the outer : inner line pairs of the amorphou
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