High field magnetization measurements on α-(BEDTTTF) 2KHg(SCN) 4

Abstract

We report torque measurements of the steady and oscillatory magnetization of α-(BEDTTTF) 2KHg(SCN) 4, where BEDTTTF is bis(ethylenedithio)tetrathiafulvalene, at temperatures down to 0.4 K in magnetic fields around at the magnetic phase transition at 24 T, the so called kink transition. The effective cyclotron mass changes only slightly at the kink transition being m ∗= m m e =1.77 ( m e is the free electron mass) above 24 T and m ∗–1.7 at 20 T for a magnetic field perpendicular to the highly conducting ac plane ( Θ=0°). For Θ=60.2° we find m ∗=3.55 (B – 18 T ). In the low field state the amplitude of the oscillatory magnetization ( μ 0 M osc=7.5 × 10 −7 T) is small; this corresponds with a high Dingle temperature (3–4 K). At 24 T a strong increase in the oscillation amplitude appears accompanied by a decrease in the Dingle temperature to T D ⩽ 2 K. The steady torque shows a quadratic increase with field at low B-values and tends to saturate near the phase transition for small angles Θ. For tilt angles Θ⩾60° the typical increase of the de Haas-van Alphen amplitude at the kink transition is no longer observed, but several anomalies occur in the steady torque above 15 T; even at 27 T α-(BEDTTTF) 2KHg(SCN) 4 is in a complex magnetic groundstate.