399 research outputs found
Upper critical field measurements up to 60 T in arsenic-deficient LaO_(0.9)F_(0.1)FeAs_(1-delta): Pauli limiting behaviour at high fields vs improved superconductivity at low fields
We report resistivity and upper critical field B_c2(T) data for As deficient
LaO_(0.9)F_(0.1)FeAs_(1-delta) in a wide temperature and high field range up to
60 T. These disordered samples exhibit a slightly enhanced superconducting
transition at T_c = 29 K and a significantly enlarged slope dB_(c2))/dT = -5.4
T/K near T_c which contrasts with a flattening of B_(c2)(T) starting near 23 K
above 30 T. This flattening is interpreted as Pauli limiting behaviour (PLB)
with B_(c2)(0) approx 63 T. We compare our results with B_(c2)(T)-data reported
in the literature for clean and disordered samples. Whereas clean samples show
no PLB for fields below 60 to 70 T, the hitherto unexplained flattening of
B_(c2)(T) for applied fields H || ab observed for several disordered closely
related systems is interpreted also as a manifestation of PLB. Consequences of
our results are discussed in terms of disorder effects within the frame of
conventional and unconventional superconductivity.Comment: 4 pages, 3 figures, submitted to RHMF09 (9th International Conference
on the Research in High Magnetic Fields), Dresden, July 22-25, 200
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Magnetic-field- and temperature-dependent fermi surface of CeBiPt
The half-Heusler compounds CeBiPt and LaBiPt are semimetals with very low charge-carrier concentrations as evidenced by Shubnikov–de Haas (SdH) and Hall-effect measurements. Neutron-scattering results reveal a simple antiferromagnetic structure in CeBiPt below TN = 1.15 K. The band structure of CeBiPt sensitively depends on temperature, magnetic field and stoichiometry. Above a certain, sample-dependent, threshold field (B>25 T), the SdH signal disappears and the Hall coefficient reduces significantly. These effects are absent in the non-4f compound LaBiPt. Electronic-band-structure calculations can well explain the observed behaviour by a 4f-polarization-induced Fermi-surface modification
Review of requirements on application of proffecional standards at development educational programs
Рассматриваются необходимость и возможность использования положений профессиональных стандартов при разработке образовательных программIn the article a necessity and possibility of the use of positions of professional standards are examined at program
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Magnetic-field- and temperature-dependent fermi surface of CeBiPt
The half-Heusler compounds CeBiPt and LaBiPt are semimetals with very low charge-carrier concentrations as evidenced by Shubnikov–de Haas (SdH) and Hall-effect measurements. Neutron-scattering results reveal a simple antiferromagnetic structure in CeBiPt below TN = 1.15 K. The band structure of CeBiPt sensitively depends on temperature, magnetic field and stoichiometry. Above a certain, sample-dependent, threshold field (B>25 T), the SdH signal disappears and the Hall coefficient reduces significantly. These effects are absent in the non-4f compound LaBiPt. Electronic-band-structure calculations can well explain the observed behaviour by a 4f-polarization-induced Fermi-surface modification
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