Uncompensated Metal Research Articles

High-Field Magnetoresistance of Ordered Beta Brass

The magnetoresistance of several single-crystal specimens of ordered $\ensuremath{\beta}$-brass has been investigated in fields up to 150 kG. The purity of the samples is sufficiently high ($\frac{{\ensuremath{\rho}}_{295}}{{\ensuremath{\rho}}_{4.2}}\ensuremath{\simeq}400$) that the high-field condition is satisfied. The results indicate that ordered $\ensuremath{\beta}$-brass is an uncompensated metal and that its Fermi surface is multiply connected. Strong open orbits were observed when the field was in {110} or {100} planes, and this behavior is compatible with the Fermi-surface model predicted by augmented-plane-wave and Green's-function energy-band calculations. Evidence for the existence of higher-order open orbits and two-dimensional regions of open orbits is presented. There are certain aspects of the data which cannot be explained in terms of the theoretical model unless (a) one of the predicted open orbits is eliminated either by magnetic breakdown or by changing some of the model's dimensions, and (b) other open orbits due to magnetic breakdown are taken into account. Various possibilities for open orbits due to magnetic breakdown are considered and their implications are compared with the observed behavior.