MOSSBAUER SPECTROMETRY OF FE(CU)MB-TYPE NANOCRYSTALLINE ALLOYS .2. THE TOPOGRAPHY OF HYPERFINE INTERACTIONS IN FE(CU)ZRB ALLOYS

Changes in the microstructure, crystallization behaviour and magnetic state of Fe87.5-xCuxZr6.5 (x = 0,1) alloys upon annealing for one hour at 500-840 OC are examined by Fe-57 Mossbauer spectrometry, x-ray dif fraction and differential thermal analysis measurements. The presence of crystallites is reflected in the Mossbauer spectra taken in the tem perature range 77 K to 473 K as sharp lines which are superimposed on broad features of the residual amorphous phase. The principal crystall ine phase is identified as bcc-Fe. An early stage of crystallization i s found even after only a 500 degrees C/1 h anneal. The total fraction of crystalline phase increases as the temperature is increased. Hyper fine fields of Fe atoms positioned in grain boundaries of the crystall ites are affected by the ordered structure of the crystallites from on e side, and by the disordered amorphous arrangement from the other. Th e behaviour of this amorphous/crystalline interface zone is studied by considering two independent hyperdne-field distributions. One is attr ibuted to the interface zone and the other represents the amorphous re mainder of the original precursor. The three-dimensional distributions of hyperfine fields obtained from this fitting procedure, which was i ntroduced in part I, the previous paper, enable us-after their decompo sition into several gaussian components-to sketch a model of the topog raphy of the hyperfine interactions within nanocrystalline samples.