Figure 1

Magnetization curves in OP Bi 2212. Panel (a) shows $M$ measured up to 45 T at $T$ from 35 K to above 90 K ($T_c=86\mathrm{K}$). Below 70 K, $|M|$ decreases as $\log H$ over a very broad field interval [1], but above 70 K, $M$ vs $H$ shows anomalous features such as the separatrix $T_s$ ($\sim 85\mathrm{K}$) at which $M$ is independent of $H$ below $\sim 5\mathrm{T}$. In large $H$, $|M|$ again decreases as $\log H$. $H_{c2}(T)$, defined as where $M\to 0$, remains high at values 100–150 T even when $T_c$ is exceeded, in sharp contrast to GGL (MF) predictions (previous experiments on $M$ stop at 5 T). Panel (b) displays the strong curvature of $M$ above $T_c$ in weak $H$ ($<2\mathrm{T}$) [2]. The curves display persistent negative curvature consistent with $M\sim -H^{1/\delta }$ with a $T$-dependent $\delta (T)$ up to $\sim 105\mathrm{K}$.Reuse & Permissions