649 research outputs found
Uniaxial stress tuning of geometrical frustration in a Kondo lattice
Hexagonal CeRhSn with paramagnetic moments on a distorted Kagome lattice
displays zero-field quantum critical behavior related to geometrical
frustration. We report high-resolution thermal expansion and magnetostriction
measurements under multiextreme conditions such as uniaxial stress up to 200
MPa, temperatures down to 0.1 K and magnetic fields up to 10 T. Under uniaxial
stress along the -direction, quantum criticality disappears and a complex
magnetic phase diagram arises with a sequence of phases below 1.2 K and fields
between 0 and 3 T (). Since the Kondo coupling increases with
stress, which alone would stabilize paramagnetic behavior in CeRhSn, the
observed order arises from the release of geometrical frustration by in-plane
stress.Comment: Accepted in PRB Rapid Com
Resistivity, Hall effect and Shubnikov-de Haas oscillations in CeNiSn
The resistivity and Hall effect in CeNiSn are measured at temperatures down
to 35 mK and in magnetic fields up to 20 T with the current applied along the
{\it b} axis. The resistivity at zero field exhibits quadratic temperature
dependence below 0.16 K with a huge coefficient of the term (54
cm/K). The resistivity as a function of field shows an
anomalous maximum and dip, the positions of which vary with field directions.
Shubnikov-de Haas (SdH) oscillations with a frequency {\it F} of 100 T
are observed for a wide range of field directions in the {\it ac} and {\it bc}
planes, and the quasiparticle mass is determined to be 10-20 {\it m}.
The carrier density is estimated to be electron/Ce. In a narrow
range of field directions in the {\it ac} plane, where the
magnetoresistance-dip anomaly manifests itself clearer than in other field
directions, a higher-frequency () SdH oscillation is
found at high fields above the anomaly. This observation is discussed in terms
of possible field-induced changes in the electronic structure.Comment: 15 pages, 5 figures, to appear in Phys. Rev. B (15 Sept. 2002 issue
Evidence for short-range antiferromagnetic fluctuations in Kondo-insulating YbB12
The spin dynamics of mixed-valence YbB12 has been studied by inelastic
neutron scattering on a high-quality single crystal. In the Kondo-insulating
regime realized at low temperature, the spectra exhibit a spin-gap structure
with two sharp, dispersive, in-gap excitations at E = 14.5 and approximately 20
meV. The lower mode is shown to be associated with short-range correlations
near the antiferromagnetic wave vector q0 = (1/2, 1/2, 1/2). Its properties are
in overall agreement with those expected for a "spin exciton'' branch in an
indirect hybridization gap semiconductor.Comment: 4 pages, 4 figures ; submitted to Physical Review Letter
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