Role of point defects and their clusters for flux pinning as determined from irradiation and annealing experiments in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">YBa</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Cu</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">O</mml:mi></mml:mrow><mml:mrow><mml:mn>7</mml:mn><mml:mi mathvariant="normal">−</mml:mi><mml:mi mathvariant="normal">δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>single crystals

We present measurements of the magnetization hysteresis on neutron- and proton-irradiated ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{7\mathrm{\ensuremath{-}}\mathrm{\ensuremath{\delta}}}$ single crystals. The crystals were irradiated to fluences of 2\ifmmode\times\else\texttimes\fi{}${10}^{17}$ n ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ (${\mathit{E}}_{\mathit{n}}$&gt;0.1 MeV) and 1\ifmmode\times\else\texttimes\fi{}${10}^{16}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}2}$ (${\mathit{E}}_{\mathit{p}}$=3.5 MeV), respectively. The magnetization was measured for both field directions. We observed increases of the hysteresis by a factor of 5 at 10 K and 1 T for H\ensuremath{\parallel}c for the neutron-irradiated sample and a factor of 9 for the proton-irradiated sample. For H\ensuremath{\parallel}ab the hysteresis increased by a factor of 8 and 6, respectively. The irradiated crystals were annealed at 100, 200, and 300 \ifmmode^\circ\else\textdegree\fi{}C in air for 8 h each. The irradiation-induced decrease of ${\mathit{T}}_{\mathit{c}}$ is fully recovered after the final annealing step for both types of irradiation. The magnetization hysteresis for H\ensuremath{\parallel}ab decreases almost to its preirradiation level after annealing at 300 \ifmmode^\circ\else\textdegree\fi{}C for both types of irradiation. In contrast, for H\ensuremath{\parallel}c, 50% of the initial neutron-irradiation- and 30% of the proton-irradiation-induced enhancements of the magnetization hysteresis are still maintained after the final annealing. The differences in annealing between neutron- and proton-irradiated samples are attributed to the different amount of point defects created by these types of irradiation.

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