Creep and depinning of vortices in nontwinned YBa₂Cu₃O₆.₈₇ single crystal

• Published in: Физика низких температур
• Date: 2008
• Main Authors: Bondarenko, A.V., Zavgorodniy, A.A., Lotnik, D.A., Obolenskii, M.A., Vovk, R.V.
• Format: Article
• Language: English
• Published: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2008
• Subjects: Свеpхпpоводимость, в том числе высокотемпеpатуpная
• Online Access: https://nasplib.isofts.kiev.ua/handle/123456789/117334
• Journal Title: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Cite this: Creep and depinning of vortices in nontwinned
 YBa₂Cu₃O₆.₈₇ single crystal
 / A.V. Bondarenko, A.A. Zavgorodniy, D.A. Lotnik,
 M.A. Obolenskii, R.V. Vovk // Физика низких температур. — 2008. — Т. 34, № 7. — С. 645–652. — Бібліогр.: 41 назв. — англ.

We present the results of transport study of vortex dynamics in YBa₂Cu₃O₆.₈₇ crystals in the magnetic field
 H||c. In low magnetic fields, H<4 kOe, the measurements were performed in the range of vortex velocities
 v=10⁻⁴–2 m/s, which covers thermal creep and flux flow modes. The pinning force Fp nonmonotonically depends
 on magnetic field in both modes, though low-field minimum in the Fp(H) curve shifts to higher fields
 with increased velocity v, that is interpreted as partial ordering the vortex lattice. The increase of the pinning
 force Fp upon increasing the field, which is observed in the flux flow mode in fields H≥3 kOe, is interpreted
 by presence of finite transverse barriers. The barriers result in preserving the entangled vortex solid phase for
 the above-barrier vortex motion along the action of the Lorentz force. We also show that field variation of the
 depinning current has a single maximum, while field variation of the pinning force inside deep creep mode has
 two maxima. Appearance of two maxima is associated with nonmonotonous field variation of the activation
 energyUpl, which corresponds to plastic vortex creep mediated by motion of the dislocations.