de Haass – van Alphen Effect

Concepts

The dHvA effect is a quantum mechanical effect in which the magnetic moment of a pure metal crystal oscillates with increasing applied magnetic field. It is used to study the volume and structure of the Fermi surface of a material.

Experiment Method

In our lab, the system contains a capacitance bridge with a cantilever for magnetometry. In order to detect a small change in the capacitance, a Wheatstone bridge circuit is used in the experiment. A schematic diagram of the cantilever is shown above. Two sensitive capacitance measurements are used to detect the small changes of the cantilever position. Upon applying a magnetic field , the change in the susceptibility will cause an inflection of the cantilever. This can be picked by the AH2700a device which is an accurate capacitance bridge and works over a frequency range of 50Hz-20kHz.