Rw. Heussner et al., ARTIFICIAL PINNING CENTER NB-TI SUPERCONDUCTORS WITH ALLOYED NB PINS, IEEE transactions on applied superconductivity, 7(2), 1997, pp. 1142-1145
A magnetic interaction has been proposed as the dominant fluxon-defect
interaction in conventional and artificial pinning center (APC) Nb-Ti
, emphasizing the proximity length (xi(N)) of the pinning center as th
e important parameter for optimizing the high field critical current d
ensity. We have characterized APC composites containing 25 vol.% of Nh
pins alloyed with 7.5 wt.% Ta and 10 wt.% W to deliberately test the
predictions of this model. We found that the bulk flux pinning force o
f the Nb10W-pin composite (xi(N)(Nb10W)similar to 32 nm) exhibited a m
agnetic field (H) and pin size (d(p)) dependency that is more consiste
nt with conventionally processed Nb47Ti (xi(N)(alpha-Ti)<32 nm) than w
ith existing pure Nb-pin APC composites (xi(N)(Nb)similar to 83 nm). T
he Nb7Ta-pin composite (xi(N) similar to 59 nm) had intermediate F-p(H
,d(p)) behavior, thus qualitatively supporting the model.