161 research outputs found
Local Magnetic Inhomogeneities in Lightly Doped BaFeAs
We report As NMR measurements in BaFeAs doped with Ni. Like
Co, Ni doping suppresses the antiferromagnetic and structural phase transitions
and gives rise to superconductivity for sufficiently large Ni doping. The spin
lattice relaxation rate diverges at , with a critical exponent consistent
with 3D ordering of local moments. In the ordered state the spectra quickly
broaden inhomogeneously with doping. We extract the average size of the ordered
moment as a function of doping, and show that a model in which the order
remains commensurate but with local amplitude variations in the vicinity of the
dopant fully explains our observations.Comment: 4 pages, 4 figure
Unconventional and conventional quantum criticalities in CeRhIrIn
An appropriate description of the state of matter that appears as a second
order phase transition is tuned toward zero temperature, {\it viz.}
quantum-critical point (QCP), poses fundamental and still not fully answered
questions. Experiments are needed both to test basic conclusions and to guide
further refinement of theoretical models. Here, charge and entropy transport
properties as well as AC specific heat of the heavy-fermion compound
CeRhIrIn, measured as a function of pressure, reveal two
qualitatively different QCPs in a {\it single} material driven by a {\it
single} non-symmetry-breaking tuning parameter. A discontinuous sign-change
jump in thermopower suggests an unconventional QCP at accompanied by
an abrupt Fermi-surface reconstruction that is followed by a conventional
spin-density-wave critical point at across which the Fermi surface
evolves smoothly to a heavy Fermi-liquid state. These experiments are
consistent with some theoretical predictions, including the sequence of
critical points and the temperature dependence of the thermopower in their
vicinity.Comment: 21+3 pages, 4+2 figures. Change the title, figures et a
Temporomandibular disorders and oral features in idiopathic inflammatory myopathies (Iims) patients: An observational study
Aim: Inflammatory idiopathic myopathies (IIMs) are inflammatory processes affecting skeletal musculature and extramuscular organs. Temporomandibular disorders (TMD) involve jaw muscles and temporomandibular joint. The aim of this observational study was to investigate the prevalence of the main TMD symptoms and signs as well as oral implications in IIM patients. Methods: The study group included 54 patients (42 women and 12 men), 22 of whom affected by dermatomyositis (DM), 29 by polymyositis (PM) and 3 by inclusion body myositis (IBM). A group of 54 patients not affected by this disease, served as CG. Oral and TMD signs and symptoms were evaluated by means of a questionnaire and through clinical examination. Results: About oral symptoms, the study group complained more frequently dysgeusia, with loss of taste or unpleasant taste (p<0.0001) and feeling of burning mouth (9.4% versus 0 controls). Xerostomia was more prevalent in the study group respect to the CG (p<0.0001). Dysphagia was reported by 48.1% of IIM patients while was absent in CG (p<0.0001). About oral signs, cheilitis (p<0.05) and oral ulcers (p<0.05) were significantly more frequent in CG. As regard to TMD symptoms, arthralgia and tinnitus didn’t showed significant differences between the two groups, while neck/shoulders and masticatory muscle pain was significantly more referred in IIM patients than in the CG (p<0.05). About TMJ signs, sounds were overlapping in the two groups: click=11.1% in both IIM patients and CG (p<0.05), crepitation in 11.1% of IIM and 9.3% of controls (p>0.05). No significant difference was detected about deflection (9.3%, p>0.05), while deviation was wider in CG (p>0.05). Active opening and lateralities showed no significant differences, while endfeel was significantly increased in IIM group for a higher presence of muscular contracture. Bruxism was present only in CG. Conclusion: The data collected from this observational study seem to support the existence of a relationship between the prevalence of TMD symptoms and signs as well as oral features in patients with myositis. A remarkable reduction of salivary flow and dysphagia were more frequent and severe in IIM patients, as well as muscle contracture and myofacial pain evoked by palpation, this result being highly significant
NMR evidence for inhomogeneous glassy behavior driven by nematic fluctuations in iron arsenide superconductors
We present As nuclear magnetic resonance spin-lattice and spin-spin
relaxation rate data in Ba(FeCo)As and
Ba(FeCu)As as a function of temperature, doping and
magnetic field. The relaxation curves exhibit a broad distribution of
relaxation rates, consistent with inhomogeneous glassy behavior up to 100 K.
The doping and temperature response of the width of the dynamical heterogeneity
is similar to that of the nematic susceptibility measured by elastoresistance
measurements. We argue that quenched random fields which couple to the nematic
order give rise to a nematic glass that is reflected in the spin dynamics.Comment: Accepted to Physical Review
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