Positron annihilation in γ-irradiated amorphous iron alloys

One-dimensional angular correlation of annihilation radiation was measured in a series of amorphous (Fe100-xCrx)85B15 alloys (x = 0-32) exposed to ,-irradiation from intensive "Co source. The relevant shape parameters were compared with those in non-irradiated alloys. Irradiation-induced changes of those parameters were found to depend on Cr contents x. The opposite signs of these changes were observed in x 4 ranges, while near x = 4 the parameters stayed unchanged. We try to interpret the results assuming that γ-quanta are able to knock out boron atoms from their positions into large cavities, thus preventing positron trapping. The crystalline embryos mode1 of amorphous alloys suggested by Hamada and Fujita is also used for explanation of the observed effects. PACS numbers: 61.43.Dq, 61.80.Ed, 78.70.Bj