Study of dHvA effect in the superconducting mixed state of CeRu₂

We have succeeded in growing high-quality single crystals of CeRu₂ and have observed dHvA oscillations both in the normal and superconducting mixed states. The detected dHvA frequencies, i.e. extremal cross-sectional areas of Fermi surfaces have been well explained by band structure calculations. The dHvA frequency between the normal and superconducting states does not change in magnitude, while the Dingle temperature increases in the mixed state. The cyclotron mass is found to become a little smaller in the mixed state than in the normal state.