The Hall Effect in a Bismuth Crystal

The Hall effect has been measured in plates cut in different directions from a single large crystal of bismuth. At room temperatures when the field $H$ is perpendicular to the trigonal axis, a negative Hall coefficient $R$ is obtained, decreasing from about 15 for $H=1000\mathrm{}$ gauss to about 7 for $H=8000\mathrm{}$. For $H$ parallel to the trigonal axis a positive coefficient of about unity is obtained, increasing slightly with the field. At -186°C $R$ is positive for all orientations of the axis and decreases as $H$ increases. The maximum $R$ observed at -186°C was + 15 at $H=600\mathrm{}$. A plate made of compressed bismuth powder gave $R=+7\mathrm{}$, approximately, at -186°C. Beckman found large negative values of $R$ for similar plates at this temperature. The Hall e.m.f. cannot be resolved into positive and negative components at -186°C in the way suggested by Becquerel.