The paramagnetic susceptibility of face-centred cubic silver-manganese and silver-tin-manganese alloys

Abstract

The variation with temperature of the paramagnetic susceptibility of 24 alloys of the silver-manganese and silver-tin-manganese systems has been investigated, and shown to obey a Curie-Weiss relationship in the temperature range 300 to 700 °K for compositions less than 17 to 18 atomic per cent manganese. The changes in the experimentally derived values of the Bohr magneton number and the Weiss constant θ as the manganese concentration is increased are discussed in terms of the effects of variation in electron concentration and lattice spacings on the electronic configuration of manganese in solid solution. It is suggested that the observed maxima in the curves of p eff against atomic per cent tin along lines of constant maganese content in the ternary system result from two competing effects, in which increasing electron concentration reduces the magnetic moment per manganese atom as a consequence of increased occupancy of 3d virtual bound states, while lattice expansion causes electron transfer from 3d states to the conduction band, resulting in an increase in the Bohr magneton number. Possible effects of an increase in the number of direct d-d interactions between nearest neighbour manganese atoms as their concentration increases, and the limitations of the localized electron treatment as applied to alloys rich in manganese, are briefly discussed.