Some thermo- and galvanomagnetic properties of a bismuth crystal
Banta, H. E.
Doctor of Philosophy
The fractional changes, due to a magnetic field, in the electrical conductivity, in the thermal conductivity, and in the thermoelectric power of a single bismuth crystal are measured in these experiments. These changes are determined as a function of the field strength, of the direction of the field, of the direction of the crystal axis, and of the direction of the heat and electric currents through the crystal. An electric current sent through the crystal cools one junction and heats the other by the Peltier effect. The temperature difference thus produced gives rise to a thermal e.m.f. in the crystal circuit. Observations of this e.m.f. allow the calculation of the fractional changes produced in the thermal conductivity and in the thermoelectric power. The change of electrical conductivity is influenced much more strongly by the crystal structure than is the change of thermal conductivity. Crystal structure and orientation of the magnetic field both affect strongly the change in the thermoelectric power. The theory of electrons in metals in its present form does not give an adequate explanation of the results. If the magnetic field changes the free electron density in bismuth some of the results may be explained in a general way.