A. Rastogi et al., Hysteretic magnetization in micron-thick YBa2Cu3O7-delta films in nearly parallel magnetic fields, PHYS REV B, 62(21), 2000, pp. 14452-14460
In an attempt to characterize hysteresis losses in micron-thick and c-axis-
oriented YBa2Cu3O7-delta films, we studied their magnetization behavior in
moderately low magnetic fields (H less than or equal to 0.1 T) oriented nea
r the nb plane (0 degrees less than or equal to theta less than or equal to
10 degrees, theta is the angle between the ab plane and the applied field)
. It is demonstrated that for the field oriented very close to the ab plane
(0 degrees less than or equal to theta less than or equal to 2 degrees), t
he magnetization is dominated by its component along the nb plane (M-ab) Th
e angular dependence of magnetization M(theta) followed the equation M(thet
a) = M-ab cos theta + M-c, sin 8, where M, is the magnetization due to the
screening currents in the nb plane. M, was estimated by (1) the transverse
magnetization that is equal to M-c for small theta values, and by (2) measu
ring magnetization with field applied along the c axis. However, in some sa
mples, the former and M(theta) were less than the latter. We attribute it t
o flux penetration along the ab plane. The penetrating flux can induce weak
links at the grain boundaries thereby causing the screening currents to fl
ow in smaller loops.