Rotating Sample Method for Measuring the Hall Mobility

A simple apparatus is described for measuring Hall mobilities. The sample to be measured is rotated in an external dc magnetic field. The sample thus ``sees'' an ac magnetic field and ac magnetic field Hall techniques may be used. Methods are described for obtaining dc or ac Hall output voltages. Probe misalignment voltages are rejected by this technique as they are in the standard ac magnetic field method. The method yielding a dc Hall voltage enables one to use simple measurement equipment. The method yielding an ac Hall voltage has all of the advantages of the standard ac magnetic field technique yet simplifies the construction of auxiliary equipment and allows one to investigate low mobility samples in the high magnetic field region by using a powerful dc electromagnet. The increased signal level found at the higher magnetic fields might extend the useful range of Hall measurements to lower mobilities than presently measurable. The results of some Hall mobility measurements using a rotating sample are compared with the values obtained by conventional techniques.