Critical Currents at the Grain Boundary of ${\rm Sm}_{1}{\rm Ba}_{2}{\rm Cu}_{3}{\rm O}_{7-\delta}$ Film Under Oblique Magnetic Fields

We measured critical current densities $(J_{cb})$ at a [001]-tilt grain boundary (GB) of a bicrystalline ${\rm Sm}_{1}{\rm Ba}_{2}{\rm Cu}_{3}{\rm O}_{7}$ film under various magnetic fields $(H_{a})$ applied obliquely. The mis-orientation angle, $\theta$, of the [001] tilt GB was 30$^{\circ}$. $H_{a}$ was varied between $-$0.65 KOe and $+$0.65 KOe. The angle, $\phi$, between the applied fields and the film surface was varied from 0$^{\circ}$ to 90$^{\circ}$. The curves of $J_{cb}$ vs. $H_{a}$ at the different $\phi$ s were qualitatively explained by a simple formula suggested in . The formula was expressed by multiplication of the two factors which include the effects of $H_{\perp}$ and $H_{\parallel}$. One fitting parameter, $\alpha$, in this formula was large for the sample of $\theta=30^{\circ}$ in our previous paper. On the contrast, $\alpha$ for the present sample in this paper is almost zero. The absolute values of $J_{cb}$ for this sample are larger than those for the previous sample by one order of magnitude. These results indicate that the parameter, $\alpha$, closely related to the quality of GB: $\alpha$ gets smaller as the film quality at GB become better.