Novel magnet-cryostat for hall effect studies at low temperature

We describe a simple electromagnet-cryostat design in which the poles of the electromagnet enter the specimen chamber of a liquid nitrogen cryostat. The arrangement enables fields of sufficient strength and uniformity to be obtained with a moderately small diameter of pole piece and a conventional power supply. Typical measurements on a germanium specimen were made. Experimental data indicate that an improvement in field homogeneity and field strength result from the use of this design compared to conventional nonentrant designs.