High-Field de Haas-Van Alphen Studies of κ-(BEDT-TTF) ₂ Cu(NCS) ₂

Abstract

We report measurements of the de Haas-van Alphen (dHvA) effect in the quasi-two-dimensional organic metal κ-(BEDT-TTF)2Cu(NCS)2 by means of a capacitive torquemeter. The experiments were carried out in magnetic fields up to 29.5 T, at temperatures down to 0.4 K and for tilt angles θ between -35° and 80°. In the angular dependence of the fundamental frequency we observed five spin-zeros, the absolute amplitude at θ = 0° amounts to μ0M = 4·10-6 T (B = 13.8 T, T = 1.4 K). Above 15 T a series of high-frequency oscillations due to magnetic breakdown is observed. The main breakdown orbit could be detected up to θ = 55°, the angular dependence is also characterized by spin-splitting effects. We determined the effective cyclotron mass of three different breakdown orbits at θ = 5.6°. Our results are in good agreement with a simple model of magnetic breakdown. The occurrence of weak oscillations forbidden within this model is discussed.