Critical current angle-dependent measurements of thin (15nm) chemically-derived YBa 2Cu 3O 7−d films in fields to 5.5 T

Abstract

Critical current measurements were made using films of YBa 2Cu 3O 7−d prepared by a metalorganic process. The film thickness was purposely reduced to about 15 nm so that measurements of the critical current could be made at temperatures of 4.2 K with reasonable width. Magnetic fields to 5.53 T were applied parallel to the film plane and as a function of angle from that plane. The current and applied field were always orthogonal. Comparison with measurements at 77 K show that at low fields, 0.5 T, the peak in critical near H//a,b is broadened at the lower temperature. Increasing fields tend to sharpen the peak more rapidly at 4 K. Measurements with H//c show a decrease by a factor of 4 at 5.5 T and did not change during a second thermal cycle between room temperature and 4.2 K. The power law exponents were determined from the I–V data ranging from 1–150μV.