de Haas-van Alphen effect in the mixed state of LuNi₂B₂C: anisotropy and field dependence of the damping due to superconductivity

Abstract

We report observation of the de Haas-van Alphen oscillations in the mixed state as well as in the normal state of LuNi₂B₂C. Two oscillations α and η are observed in the mixed state. In particular, the α oscillation can be studied not only deep in the mixed state as a function of magnetic field but also as a function of field direction. The damping rate of the oscillations due to superconductivity is found to be very anisotropic. For fields far below H_c2, the damping behavior is anomalous and cannot be explained only in terms of the superconducting gap. We argue that both the anisotropy of the gap and a disorder of the flux line lattice are responsible for the anisotropic and anomalous behavior of the damping in the mixed state.