A de Haas-van Alphen study of niobium: Fermi surface, cyclotron effective masses, and magnetic breakdown effects

The Fermi surface of niobium has been investigated using the de Haas-van Alphen effect. Data were taken at temperatures as low as 0.3 K and in fields as high as 130 kG. An on-line minicomputer was used to Fourier-transform the digitized signals. Many new extremal area data have been obtained, including oscillations associated with the previously unobserved γ-centered hole octahedron and γ and N-centered orbits on the so-called jungle gym. An additional set of signals has been observed near [100], which are thought to be a result of magnetic breakdown between the second zone octahedron and third zone jungle gym. A separate low-frequency signal was observed and is believed to be a result of magnetic-breakdown-induced quantum interference oscillations. Anisotropies of the cyclotron effective mass have been determined for many orbits on all three of the Fermi surface sheets. Finally, the area data have been used to parametrize the Fermi surface in terms of scattering phase shifts in a Korringa-Kohn-Rostoker band structure formalism.