492 research outputs found
Optical study of interactions in a d-electron Kondo lattice with ferromagnetism
We report on a comprehensive optical, transport and thermodynamic study of
the Zintl compound YbMnSb, demonstrating that it is the first
ferromagnetic Kondo lattice compound in the underscreened limit. We propose a
scenerio whereby the combination of Kondo and Jahn-Teller effects provides a
consistent explanation of both transport and optical data.Comment: 4 page
Fermi Surface Reconstruction in CeRhCoIn
The evolution of the Fermi surface of CeRhCoIn was studied as
a function of Co concentration via measurements of the de Haas-van Alphen
effect. By measuring the angular dependence of quantum oscillation frequencies,
we identify a Fermi surface sheet with -electron character which undergoes
an abrupt change in topology as is varied. Surprisingly, this
reconstruction does not occur at the quantum critical concentration ,
where antiferromagnetism is suppressed to T=0. Instead we establish that this
sudden change occurs well below , at the concentration x ~ 0.4 where long
range magnetic order alters its character and superconductivity appears. Across
all concentrations, the cyclotron effective mass of this sheet does not
diverge, suggesting that critical behavior is not exhibited equally on all
parts of the Fermi surface.Comment: 4 pages, 4 figure
Collapse of the hyperfine magnetic field at the Ru site in ferromagnetic rare earth intermetallics
The M\"{o}ssbauer Effect(ME) is frequently used to investigate magnetically
ordered systems. One usually assumes that the magnetic order induces a
hyperfine magnetic field, , at the ME active site. This is the
case in the ruthenates, where the temperature dependence of at
Ru sites tracks the temperature dependence of the ferromagnetic or
antiferromagnetic order. However this does not happen in the rare-earth
intermetallics, GdRu and HoRu. Specific heat, magnetization, magnetic
susceptibility, M\"{o}ssbauer effect, and neutron diffraction have been used to
study the nature of the magnetic order in these materials. Both materials are
found to order ferromagnetically at 82.3 and 15.3 K, respectively. Despite the
ferromagnetic order of the rare earth moments in both systems, there is no
evidence of a correspondingly large in the M\"{o}ssbauer
spectrum at the Ru site. Instead the measured spectra consist of a narrow peak
at all temperatures which points to the absence of magnetic order. To
understand the surprising absence of a transferred hyperfine magnetic field, we
carried out {\it ab initio} calculations which show that spin polarization is
present only on the rare-earth site. The electron spin at the Ru sites is
effectively unpolarized and, as a result, is very small at
those sites. This occurs because the 4 Ru electrons form broad conduction
bands rather than localized moments. These 4 conduction bands are polarized
in the region of the Fermi energy and mediate the interaction between the
localized rare earth moments.Comment: 34 pages -Revtex + 17 ps figure
Roughness Signature of Tribological Contact Calculated by a New Method of Peaks Curvature Radius Estimation on Fractal Surfaces
This paper proposes a new method of roughness peaks curvature radii calculation and its application to tribological contact analysis as characteristic signature of tribological contact. This method is introduced via the classical approach of the calculation of radius of asperity. In fact, the proposed approach provides a generalization to fractal profiles of the Nowicki's method [Nowicki B. Wear Vol.102, p.161-176, 1985] by introducing a fractal concept of curvature radii of surfaces, depending on the observation scale and also numerically depending on horizontal lines intercepted by the studied profile. It is then established the increasing of the dispersion of the measures of that lines with that of the corresponding radii and the dependence of calculated radii on the fractal dimension of the studied curve. Consequently, the notion of peak is mathematically reformulated. The efficiency of the proposed method was tested via simulations of fractal curves such as those described by Brownian motions. A new fractal function allowing the modelling of a large number of physical phenomena was also introduced, and one of the great applications developed in this paper consists in detecting the scale on which the measurement system introduces a smoothing artifact on the data measurement. New methodology is applied to analysis of tribological contact in metal forming process
High-pressure, transport, and thermodynamic properties of CeTe3
We have performed high-pressure, electrical resistivity, and specific heat
measurements on CeTe3 single crystals. Two magnetic phases with nonparallel
magnetic easy axes were detected in electrical resistivity and specific heat at
low temperatures. We also observed the emergence of an additional phase at high
pressures and low temperatures and a possible structural phase transition
detected at room temperature and at 45 kbar, which can possibly be related with
the lowering of the charge-density wave transition temperature known for this
compound.Comment: 5 pages, 4 figure
Pressure induced superconductivity in the charge density wave compound TbTe3
A series of high-pressure resistivity measurements on single crystals of
TbTe3 reveal a complex phase diagram involving the interplay of
superconducting, antiferromagnetic and charge density wave orders. The onset of
superconductivity reaches a maximum of ~ 3.5 K (onset) near 75 kbar.Comment: 4 pages, 4 figures; magnetization figure removed due to space
constraints; accepted for publication in Physical Review Letter
Non-Fermi liquid behavior in a fluctuating valence system, the filled skutterudite compound CeRu_{4}As_{12}
Electrical resistivity , specific heat C, and magnetic susceptibility
measurements made on the filled skutterudite CeRu_4As_{12} reveal
non-Fermi liquid (NFL) T - dependences at low T, i.e., (T) T^{1.4}
and weak power law or logarithmic divergences in C(T)/T and (T).
Measurements also show that the T - dependence of the thermoelectric power S(T)
deviates from that seen in other Ce systems. The NFL behavior appears to be
associated with fluctuations of the Ce valence between 3^+ and 4^+ rather than
a typical Kondo lattice scenario that would be appropriate for an integral Ce
valence of 3^+.Comment: 18 pages, 5 figure
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