POSITRON-ANNIHILATION IN GAMMA-IRRADIATED AMORPHOUS IRON-ALLOYS

One-dimensional angular correlation of annihilation radiation was meas ured in a series of amorphous (Fe100-xCrx)85B15 alloys (x = 0-32) expo sed to gamma-irradiation from intensive Co-60 source. The relevant sha pe parameters were compared with those in non-irradiated alloys. Irrad iation-induced changes of those parameters were found to depend on Cr contents x. The opposite signs of these changes were observed in x < 4 and x > 4 ranges, while near x = 4 the parameters stayed unchanged. W e try to interpret the results assuming that gamma-quanta are able to knock out boron atoms from their positions into large cavities, thus p reventing positron trapping. The crystalline embryos model of amorphou s alloys suggested by Hamada and Fujita is also used for explanation o f the observed effects.