Hall Effects of the Cobalt Nickel Alloys and of Armco Iron

Experimental investigations of the Hall effects in cobalt, the cobalt-nickel alloys, and Armco iron are described in detail. Precision measurements were made with magnetic fields up to 30 kilogauss in order to separate the ordinary and extraordinary effects. The ordinary effect in all the Co-Ni alloys was found to be negative and agreed within a factor of two with values expected from only $4s$ band conductivity. The ordinary effect in Armco iron was positive indicating hole conduction in the $3d$ band. The field parameter $\alpha$ was observed to be small and negative for most of the cobalt rich alloys, while it was positive for the nickel rich alloys and Armco iron. The limitations in the use of the simple two-band model for explaining the data are outlined. No explanation of $\alpha$ is given.