Positron Localisation in Metallic Glasses in Terms of the Crystalline Embryo Model

Abstract

One-dimensional angular correlation studies of the Ni73TM5Si10B12 (TM=V, Cr, Mn, Fe and Co) metallic glasses have been performed. The analysis of the angular correlation data, consisting of a deconvolution into one Gaussian and two parabolic curves, indicates the possibility that two 'species' of the nearly free electrons are present in the particular materials. We have attempted to verify the physical reliability of this fitting procedure by assuming that the crystalline embryos tend to localise the thermalised positrons. It is shown that some of the estimated parameters describing the shape of the angular correlation curves systematically change with changing the atomic number of the TM admixtures. It allows the effect of TM on the thermal stability to be precisely recognised.

Positron Annihilation in γ-Irradiated Amorphous Iron Alloys

“…In order to explain this behaviour one may take into account that if AA of metal-metalloid type is doped with another transition metal having atomic number less than that of basic metal, the amorphous state turns out to become more stable. This stabilization is suggested to be caused by strengthening of metal-metalloid bonds formed by overlapping of sp hybrid orbitals of metalloid atoms with sd orbitals of transition element owing to the reduction of d-electron concentration [11]. More tight binding of B atoms, originating from addition of Cr, should decrease the probability of knocking out B atoms into cavities and, consequently, bring down the passivation effect observed in Fe85B15.…”