Figure 3.

The in-plane Hall coefficient R_H of YBCO in samples 2–6 with y = 6.30, 6.36, 6.40, 6.45, and 6.63, respectively. The profiles of R_H in samples 2 and 3 are qualitatively different from those in samples 4–6. In samples 2 and 3, R_H peaks near T_N and decreases monotonically as in Fig. 2. However, in samples 4–6 (T_N ≈ 0), the peak temperature in R_H is systematically lower as y increases beyond 6.40. All samples display a “notch” near 350 K where ρ displays a slope change.