STRUCTURAL EVOLUTION AND MAGNETIC-PROPERTIES OF NANO-GRANULAR METALLIC ALLOYS

Fe clusters have been dispersed in Ag matrices using cluster beam (CB) sources without any heat treatment. Their structure and morphology ha ve been studied by comparison with those of the sputter-deposited Fe-A g alloys using small angle X-ray scattering, high resolution transmiss ion electron microscopy and extended X-ray absorption fine structure m easurements. In the granular alloys made by CB, bcc Fe clusters of a f ew nanometers dimension are detected, together with ten-nanometer scal e geometrical and chemical fluctuations. In the sputter-deposited allo ys, the Fe atoms are rather well mixed with the Ag atoms in the as-dep osited state, and fee Fe clusters are first formed and transform to la rger bce particles with increasing annealing temperature. The field-de pendence of the magnetoresistance is well correlated with the growth m ode of the Fe clusters in the granular alloys.