An Induced Torque Study of Hg3-δAsF6

Abstract

<p> Under certain conditions, an induced torque measurement is a measure of the ratio of the resistivity to the square of the Hall constant. Induced torque measurements can be directly related to the connectivity of the Fermi surface.</p> <p> A modulation technique for measuring induced torque is justifield theoretically, and an instrument employing this technique is characterized. Operational limitations on parameters such as sample resistivity and modulation rate are specified. A new procedure is proposed to extract more information from induced torque measurements. This procedure would allow the measurement of resistivity and Hall constant of ellipsoidal samples. The procedure is untested but appears to be feasible.</p> <p> Observations of the induced torque of Hg3-δAsF6 show that the Fermi surface supports an open orbit in one direction. This is discussed in the context of a model (Razavi et al., 1979), which has Fermi surface cylinders of common direction. This is based on conduction in Hg chain directions, which lie in only two directions. At magnetic fields greater than 3.0 Tesla, magnetic breakdown is observed. A Brillouin zone constructed using Hg chain symmetry and crystal parameters yields reciprocal lattice vectors compatible with the observed magnetic breakdown. The model is confirmed but a refinement is needed to allow an undulation of the Fermi surface cylinders.</p>