Study of short range order in Fe–Ni–Si–B amorphous alloys

Mössbauer studies on a series of transition metal-metalloid metallic glasses Fe78−xNixSi8B14 with x=0,15,25,38,53,58 have been done with an aim to get information about short range order (SRO) in this system. Thermal neutron irradiation up to a dose of 1019 neutrons/cm2 has been used to perturb the SRO in the specimens. The effect of neutron irradiation is seen to increase the Curie temperature of the Ni-rich alloys. Further, the average number of metalloid near neighbours of Fe increases with increasing Ni concentration, although the metalloid concentration remains unchanged. It is suggested that also in amorphous Fe–Ni–B alloys, similar to crystalline Fe–Ni–B alloys, Ni preferentially goes to sites which have less number of B near neighbours, driving the Fe atoms to occupy the sites with larger number of B near neighbours. Irradiation partially destroys this preferential site occupancy. As observed by earlier workers, sharp variations around 40% Ni concentration in Mössbauer parameters and resistivity may at least partly be attributed to the preferential site occupancy by Ni.