Ferromagnetic Hall Coefficient of Nickel Alloys

Published Hall coefficient data for binary Ni alloys have been examined in light of the Karplus-Luttinger theory of the ferromagnetic Hall effect. This theory indicates that the extraordinary Hall coefficient is related to the square of the electrical resistivity, $R_1=A{\rho }^2$. Neither the exponent nor the coefficient of $\rho$ varies as additions of up to 30 atomic percent Cu are made to pure Ni, and as the temperature is varied from 20°K to 290°K. On the other hand, small additions of either Al, Si, or Sn to Ni cause a significant variation in $A$, but appear to leave the exponent of $\rho$ unaltered. A tentative explanation is offered for the difference in behavior.