Electrical and thermal magnetoconductivities of single-crystal beryllium at low temperatures and its use as a heat switch

Abstract

The effects of transverse magnetic fields up to 955 kA/m (12 kOe) on the electrical and thermal conductivities of single-crystal beryllium have been measured between 2 and 300 K. Most of the measurements were made on a sample with a resistance ratio of1340. This sample was pure enough so that the intrinsic electronic thermal resistivity could be measured for the first time. It was found to have the usual T² behavior. The current and heat flow were along the hexagonalc axis of the crystal, while the thermal and electrical conductivities were studied as a function of the angle of the magnetic field in the basal plane. Below about 50 K the thermal conductivity could be reduced by several orders of magnitude by applying the magnetic field. The lattice conductivity, extrapolated from the measurements in the magnetic field, is given by k =γT², where γ=1.6×10⁻⁴ W/cm K³. This value is in reasonable agreement with that obtained from measurements of beryllium alloys. The use of single-crystal beryllium as a heat switch for temperatures below about 30 K is discussed.