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J Wosnitza

Publications and source records attributed to J Wosnitza.

15 recordsLinked to original sources
PubMed2005

Magnetic-field-induced band-structure change in CeBiPt.

We report on a field-induced change of the electronic band structure of CeBiPt as evidenced by electrical-transport measurements in pulsed magnetic fields. Above approximately 25 T, the charge-carrier concentration increases nearly 30% with a concomitant disappearance of the Shubnikov-de Haas signal. These features are intimately related to the Ce 4f electrons since for the non-4f compound LaBiPt the Fermi surface remains unaffected. Electronic band-structure calculations point to a 4f-polarization-induced change of the Fermi-surface topology.

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PubMed2001

Field-induced metal-insulator transition in a two-dimensional organic superconductor.

The quasi-two-dimensional organic superconductor beta"-(BEDT-TTF)2SF5CH2CF2SO3 (Tc approximately 4.4 K) shows very strong Shubnikov-de Haas (SdH) oscillations which are superimposed on a highly anomalous steady background magnetoresistance, Rb. Comparison with de Haas-van Alphen oscillations allows a reliable estimate of Rb which is crucial for the correct extraction of the SdH signal. At low temperatures and high magnetic fields insulating behavior evolves. The magnetoresistance data violate Kohler's rule, i.e., cannot be described within the framework of semiclassical transport theory, but converge onto a universal curve appropriate for dynamical scaling at a metal-insulator transition.

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PubMed2000

Chiral critical exponents of the triangular-lattice antiferromagnet CsMnBr3 as determined by polarized neutron scattering

The critical exponents gamma(c) = 0.84(7) of the chiral susceptibility above the Neel temperature, T(N), and beta(c) = 0. 44(2) of the average chirality below T(N) have been determined for the triangular-lattice antiferromagnet CsMnBr3 by means of polarized neutron scattering. These first experimental values of chiral critical exponents are in line with theoretical predictions and fulfill their scaling relation. The temperature at which the average chirality appears coincides with the spin-order transition temperature, T(N).

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PubMed2000

kappa-(BEDT-TTF)2Cu[N(CN)(2)]Br: a fully gapped strong-coupling superconductor.

High-resolution specific-heat measurements of the organic superconductor kappa-(BEDT-TTF)(2)-Cu[N(CN)(2)]Br in the superconducting ( B = 0) and normal ( B = 14 T) states show a clearly resolvable anomaly at T(c) = 11.5 K and an electronic contribution, C(es), which can be reasonably well described by strong-coupling BCS theory. Most importantly, C(es) vanishes exponentially in the superconducting state which gives evidence for a fully gapped order parameter.

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