Anisotropic specific heat behavior of textured YBa2Cu3O7 under a magnetic field

doi:10.1016/0921-4534(90)90043-E

Physica C: Superconductivity

Volume 166, Issues 5–6, 1 April 1990, Pages 451-455

https://doi.org/10.1016/0921-4534(90)90043-E Get rights and content

Abstract

Measurements of specific heat as a function of temperature, under various magnetic fields parallel or normal to the (a, b) plane, have been carried out on highly textured YBa₂Cu₃O₇ samples. The samples have been prepared by creep-sintering and characterized by X-ray diffraction, magnetisation and resistivity. We observe that the effect of a magnetic field on the specific heat anomaly at T_c is strongly anisotropic: namely when the field is normal to the (a, b) plane the specific heat peak almost vanishes at 6 T whereas the same field hardly affects the specific heat when parallel to the (a, b) plane.

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The specific heat of a single crystal of YBa₂Cu₃O₇ was measured by adiabatic calorimetry between 40 and 150 K. The typical scatter of the data is well below 0.1%. Fields up to 20 T were applied either parallel or perpendicular to the c-axis. The shape of the anomaly at T_c changes with the magnetic field in the same manner for both directions, within a scale factor that determines the bulk anisotropy ratio, 5.5 ± 0.5, for (dH_c2/dT)_Tc. The superconducting transition is still observable in 20 T. A growing mixed-state Maki term is present. The characteristic non-classical behavior of YBa₂Cu₃O₇ in a field, featuring a considerable smearing of the transition and an apparently field-independent onset, may be qualitatively understood as a phenomenological consequence of the small and anisotropic value of the coherence length ξ alone, using the relevant models of field-induced critical 1D fluctuations on the one hand, and a London-like regime for the mean-field part of the transition on the other hand.
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^∗: Permanent address: Laboratoire d'Optique Physique ESPCI, 10, rue Vauquelin, 75231 Paris, France.

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Anisotropic specific heat behavior of textured YBa2Cu3O7 under a magnetic field

Abstract

Physica C

Phys. Rev.

J. Supercond.

Phys. Rev. Lett.

Phys. Rev.

9th Gen. Conf. Cond. Matt. E.P.S. Nice

Soviet. Phys. JETP

Physica C

Anisotropic specific heat behavior of textured YBa₂Cu₃O₇ under a magnetic field