dHvA oscillation in the superconducting mixed state of CeRu₂

We have succeeded in growing a high-quality single crystal of CeRu₂ and dHvA oscillations have been clearly observed both in the normal and mixed states. The dHvA amplitude of a small dHvA frequency is reduced a little in the mixed state compared to that in the normal state, while that of a large dHvA frequency is reduced strongly. The cyclotron mass is found to become a little smaller in the mixed state than that in the normal state, although the cross-sectional area of the Fermi surface is unchanged from the normal state.