Effects of defect morphology on the properties of the vortex system inBi2Sr2CaCu2O8+δirradiated with heavy ions

Abstract

To study the effects of defect morphology on vortex dynamics, reversible magnetization, and c-axis magnetoresistance, ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}{\mathrm{CaCu}}_{2}{\mathrm{O}}_{8+\ensuremath{\delta}}$ single crystals are irradiated with heavy-ions; ${0.7\ensuremath{-}\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{}}^{84}\mathrm{Kr},$ ${3.5\ensuremath{-}\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{}}^{136}\mathrm{Xe},$ ${3.8\ensuremath{-}\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{}}^{181}\mathrm{Ta},$ and ${3.1\ensuremath{-}\mathrm{G}\mathrm{e}\mathrm{V}\mathrm{}}^{209}\mathrm{Bi}.$ First, defect morphology is investigated by transmission electron microscope (TEM) observations, which reveals that the fluctuation of defect radius along the ion path increases with decreasing the electronic-stopping power for the incident ion ${S}_{e}.$ The frequency dependence of the loss-peak temperature, where the imaginary part of ac susceptibility reaches a maximum, shows that the power-law behavior of a Bose-glass transition appears only for the irradiation with $〈{S}_{e}〉\ensuremath{\gtrsim}1.9\mathrm{keV}/\AA{},$ where $〈{S}_{e}〉$ is the mean value of ${S}_{e}$ in the sample. The magnetic-field dependence of reversible magnetization clearly shows the feature of the recoupling of vortices along the c axis only for Ta and Bi irradiations with $〈{S}_{e}〉\ensuremath{\gtrsim}3.3\mathrm{keV}/\AA{}.$ The magnetoresistance along the c axis also reveals that the recoupling of vortices caused by the production of columnar defects takes place when $〈{S}_{e}〉\ensuremath{\gtrsim}3.3\mathrm{keV}/\AA{}.$ The present results demonstrate that the fluctuation in the defect radius along the ion path suppresses the Bose-glass transition and the recoupling of vortices along the c axis.