Anisotropic properties of the anomalous second peak in the magnetization curves and the irreversibility field have been investigated by magnetic measurement for YBa2Cu3O7 (6.6 ≤ y ≤ 6.9) single crystals in magnetic fields up to 55 kOe. The angular dependence of the magnetic field Hp at which the second peak appears is well described by the Ginzburg-Landau effective-mass model. This behavior results from the anisotropic vortex structure dominated by the effective mass of superconducting electrons. However, the anisotropic behavior of the irreversibility field Hirr is given by an extended expression, Hirr ln Hirr ∞ 1/(cos2θ + γ-2sin2θ) 1 2, which is proposed by taking account of the influence of the flux creep on the irreversibility field. The anisotropic parameter γ is consistently estimated from the angular dependence of both characteristic fields of Hp and Hirr. The γ value increases with decreasing oxygen content indicating the suppression of the interlayer coupling between CuO2 superconducting layers by reducing oxygen.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Energy Engineering and Power Technology
- Electrical and Electronic Engineering