I. Deckers

Experimental techniques for pulsed magnetic fields

Abstract Recent developments at the K.U. Leuven pulsed field laboratory are reviewed. This includes new 60 T user magnets, pulse shaping, decentralized data recording for multiple experiments, low temperature cryogenics, vibration damping, rotatable sample holders and sensitive magnetization measurements. Experimental results (on semiconductors, super-conductors and organic conductors) are shown to illustrate the improvements in the experimental techniques.

The K.U. Leuven pulsed high magnetic field facility

Abstract The pulsed field installation at the K.U. Leuven is upgraded for the development and use of the new generation of high performance coils with peak fields in the 60–70 T range. New equipment includes an improved coil winding installation, capacitor bank switchgear and electrical diagnostics to enable the running of two experiments in parallel, new cryostats for stabilized temperatures in the 300–0.4 K range, sample holders whixh permit rotation of the sample, and facilities for sample preparation.

Strong pulsed magnetic fields combined with very low temperatures

Abstract New types of pulsed field coils have been developed: optimized reinforcement by fibre composites has yielded ultimate peak fields of 67T in a 12 mm bore and 58T in a 20 mm bore, and a coil made with a newly developed cable of pearlitic steel wires around a copper core has reached 55T in a 17 mm bore. The temperature range of pulsed field experiments has been extended into the 400 mK range by means of top-loading 3He cryostats. Experiments with the fractional quantum Hall effect have shown that sample heating due to eddy currents can be kept within acceptable limits but it becomes critical for a pulse duration of 10 ms or less.

Magnetic breakdown and quantum interference in the quasi-two-dimensional superconductor κ-(BEDT-TTF)2Cu(NCS)2

Abstract With the aid of numerical modelling and recent pulsed magnetic field experiments, we discuss the applicability of the established magnetic breakdown and quantum interference theories to κ-(BEDT-TTF)2Cu(NCS)2. We pay particular attention to the possible origin(s) of the ‘β-α’ frequency, which is forbidden in the classical breakdown picture.

Chiral Fermi liquids and a new version of the quantum Hall effect observed in organic conductors at very high magnetic fields

We present evidence for a new form of quantum Hall effect (QHE) in organic molecular metals, in which the chemical potential is pinned to quasi-one-dimensional states between sharp quasi-two-dimensional Landau levels over finite regions of magnetic fields. A dramatic change in the behaviour of the resistivity component rho(zz) occurs when the QHE is observed, suggesting the presence of a chiral Fermi liquid at the sample edges

The quantum Hall effect and chiral Fermi liquids in a quasi-two-dimensional organic conductor at very high magnetic fields

The oscillations in the longitudinal magnetoresistance of alpha-(BEDT-TTF)(2)KHg(SCN)(4) are shown to be strongly attenuated with decreasing temperature if the sample is in a state where it displays the quantum Hall effect. We provide evidence that this is a direct consequence of the existence of a chiral Fermi liquid on the surface of the sample

Magnetic-field dependent Fermi surfaces in quasi-2D organic conductors

We review recent studies of charge-transfer salts of the ion bis(ethylenedithio)tetrathiafulvalene which exhibit spin-density wave ground states, concentrating on techniques involving high magnetic fields and experiments carried out by the oxford group and coworkers.

A 3He installation for the study of the FQHE in pulsed magnetic fields

Abstract Details are given of a specially designed 3 He cryostat in combination with a 50T pulsed high field coil. This combination has been used for magnetotransport experiments of the fractional quantum Hall effect (FQHE) in GaAs/AlGaAs heterojunctions in the extreme quantum limit.

Calculations of quantum oscillations in quasi-two-dimensional charge-transfer salts

A numerical model is used to derive the quantum oscillations in the magnetisation and magnetoresistance of quasi-two-dimensional α-phase BEDT-TTF charge-transfer salts in high magnetic fields. Recent experimental results are simulated and the standard Lifshitz-Kosevich formalism is shown to be no longer appropriate.

Magnetotransport Investigation of HgSe:Ce in High Magnetic Fields

Oscillations of the transverse magnetoresistance and the Hall voltage in HgSe:Ce are studied at temperatures between 1.2 K and 77 K, in magnetic fields up to 35 T. From the Shubnikov-de Haas measurements band structure parameters are calculated and compared to the values for HgSe. Due to scattering effects SdH-like oscillations are observed in the Hall voltage. Resistivity measurements show a minimum in the temperature dependence.