Perfect fits of J(c)-B dependencies in NEG-123 bulk samples with 30% Gd-211 fine particles

Magnetization hysteresis loops (MHL) were measured on two NEG-123 bulk samp les with addition of 30% Gd-211 fine (sub-micron) particles in the temperat ure range 65-88 K. These two samples possessed significantly different seco nd-to-central peak heights ratios, Both sets of the J(c)-B curves could be, however, fitted with a high precision by the same combined analytical func tion J(c)(B) = J(cp) exp(-alphaB/B-p) + J(sp)b(p) exp[(1 - (B/B-p)(n))/n] i n all investigated temperatures. The pinning regimes governing formation of the central and second peak could be separated in this way. As far as the central peak contribution to the MHL becomes usually negligible at around B -p, the shape of J(c)(B) above B-p is governed by only a high-field pinning mechanism. The central peak extends to this field region only at temperatu res very close to T-c. Good scaling of the pinning force density with tempe rature gives a further support to the above conclusions. (C) 2001 Elsevier Science B.V. All rights reserved.