Conduction Electrons in Pseudonickel Alloys from Hall Data

The two Hall coefficients and resistivity of four Ni-Cu-Fe alloys having 28 electrons per atom, with Ni content from 97 to 70 atomic percent, have been measured at 20°K, 77°K, and room temperature using fields up to 3.1 webers/${\mathrm{meter}}^2$. $R_0$ is found to increase with decreasing temperature for all compositions, and also to increase with decreasing Ni content for each of the three temperatures measured. The effective number of conduction electrons calculated from the $R_0\text{'}\mathrm{s}$ measured at low temperatures is found to fall smoothly from the anomalous peak at pure Ni to about 0.3 at 70% Ni, in agreement with the predictions of the four-band model. A short summary of the considerable evidence supporting this model is given. The extraordinary Hall coefficient, $R_e$, is negative at all temperatures for the three samples richest in Ni, being increasingly negative as the Ni content is lowered. On the other hand, the 70% Ni-20% Cu-10% Fe alloy has positive extraordinary Hall coefficients at all temperatures. The behavior of $R_e$ obeys none of the variously proposed theoretical relations.