Superconducting and anomalous electron transport properties and electronic structure of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">BaNbO</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ba</mml:mi></mml:mrow>

Gasparov, V. A.; Ermolov, S.N.; Струкова, Г. К.; Sidorov, N. S.; Khassanov, S. S.; Wang, H.-S.; Schneider, Meike; Glaser, E.; Richter, W.

doi:10.1103/physrevb.63.174512

Cited by 20 publications

(10 citation statements)

References 28 publications

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“…In contrast to the conventional BCS theory [50], H c2 (T) dependence is linear over an extended temperature range with no evidence of saturation down to 0.35 K. Similar linear H c2 (T) dependence have been observed in MgB 2 [51,52] and BaNbO x [53] compounds. One can describe this behavior of upper critical filed using two-gap approach.…”

Section: Upper and Lower Critical Magnetic Fieldsupporting

confidence: 59%

Two-gap superconductivity inZrB12: Temperature dependence of critical magnetic fields in single crystals

2006

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We report the measurements of the temperature dependence of the resistivity, ρ(T), magnetic penetration depth, λ(T) the lower, H c1 (T), and upper, H c2 (T), critical magnetic fields, for single crystals of dodecaboride ZrB 12 , diboride ZrB 2 and thin films of diboride MgB 2 . We observe a number of deviations from conventional behavior in these materials. Although ZrB 12 behaves like a simple metal in the normal state, the resistive Debye temperature, 300 K, is three times smaller relative to that (800-1200 K) calculated from the specific heat, C(T), data. We observe predominantly quadratic temperature behavior of resistivity in ZrB 12 below 25 K, and in ZrB 2 below 100 K, indicating the possible importance of the electron-electron interaction in these borides. Superfluid density of ZrB 12 displays unconventional temperature dependence with pronounced shoulder at T/T c equal to 0.65. Contrary to conventional theories we found a linear temperature dependence of H c2 (T) for ZrB 12 from T c down to 0.35 K. We suggest that both λ(T) and H c2 (T) dependencies in ZrB 12 can be explained by two band BCS model with different superconducting gap and T c .

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Section: Upper and Lower Critical Magnetic Fieldsupporting

confidence: 59%

Two-gap superconductivity inZrB12: Temperature dependence of critical magnetic fields in single crystals

2006

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“…Considerable effort has gone into the production of this conductive oxide in both the bulk polycrystalline [5][6][7][8] and thin film forms. [9][10][11][12][13][14] The results obtained show wide discrepancies with regard to the transport properties as well as to the degree of niobium solubility within the BaTiO 3 structure. Further interest in this material stems from reports of superconductivity 10 as well as magnetic anomalies attributed to spin-singlet small bipolarons.…”

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confidence: 50%

Structural and transport properties of epitaxial niobium-doped BaTiO3 films

Shao

Hughes

Dąbkowski

et al. 2008

Applied Physics Letters

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Ba Ti 1 − x Nb x O 3 films, spanning the entire range of x, have been deposited on MgAl2O4 substrates. X-ray diffraction measurements indicate single phase films for all values of x, contrary to a previously reported niobium solubility limit. Films show extreme sensitivity to high temperature oxygen exposure, which destroys conductivity and severely disrupts crystallinity. Under optimum growth conditions increasing x gives rise to a Ti4+ to Ti3+ transformation in the oxidation state accompanied by increased conductivity with a semiconductor-metal transition near x=0.2. Temperature dependent magnetic measurements show an anomalous rise in the spin moment, a feature supportive of the small singlet bipolaron model.

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“…6 for the x ¼0.20 sample; however, even a small loss of oxygen corresponding to d¼0.1 (or a 3.33% deviation from stoichiometry) would be sufficient to compensate for this deviation. The loss of oxygen ions has also been reported for BaNbO 3 À d thin film [27] where d¼0.6-0.8.…”

Section: Discussionmentioning

confidence: 78%