de Haas-van Alphen Effect in Iridium

The de Haas-van Alphen effect has been used to study the extremal areas, cyclotron masses and spin-splitting nulls on the two $\Gamma$-centered sheets of the Fermi surface of iridium for the magnetic field in a (110) plane. The measured extremal areas are in good agreement with recent relativistic-augmented-plane-wave calculations by Andersen. The massenhancement factor determined from a comparison of the calculated and measured masses was found to be 1.31 and rather isotropic for the $\Gamma 6$ sheet; the enhancement on the $\Gamma 5$ sheet is distinctly more anisotropic.