Critical magnetic-field angle for high-field current transport in YBa2Cu3O7 at 76 K

✍ Scribed by J.W. Ekin

• Publisher: Elsevier Science
• Year: 1992
• Tongue: English
• Weight: 319 KB
• Volume: 32
• Category: Article
• ISSN: 0011-2275
• DOI: 10.1016/0011-2275(92)90033-7

✦ Synopsis

High magnetic field (0.5 T to 9 T) measurements of the in-plane transport critical current density Jc of YBa2Cu307 at liquid nitrogen temperature are reported as a function of the orientation of magnetic field B with respect to the a,b-plane. In contrast to earlier results at lower fields (< 3 T), the measurements reported here at high fields reveal a Jc versus angle curve with a head-and-shoulders shape with two angular regions having distinctly different behaviour. For magnetic field oriented close to the a,b-plane, a sharp, narrow intrinsic-pinning peak in Jc about the B _L c-axis is observed; on either side of the peak, Jc is still relatively high (-104A cm -a) and nearly independent of magnetic field magnitude and angle. However, beyond a critical angle 8 c, the Jc versus 8 dependence crosses over to a markedly different behaviour, characterized by a decrease in the sharpness of the voltage-current characteristic and a rapid decrease in Jc. The critical angle 8 c where this change occurs is determined experimentally from the sharp break in the Jc versus 8 curve at the edge of the shoulders, defined by the angle where the minimum in dZJc/dO "~ occurs. Characteristic values of/9 c for oriented-grained YBa2Cu307 at 76 K are ±39 ° at 5 T, ±24 ° at 7 T and ±17 ° at 9 T (where 0 -0 for B in the a,bplane). To take advantage of the high, nearly field-independent Jc on either side of the intrinsic pinning peak, magnet design will need to allow an adequate angular margin to avoid the pinning transition at 8c.