Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Strongly nonlinear magnetization above $T_c$ in $\rm
  Bi_2Sr_2CaCu_2O_{8+\delta}$   Using high-resolution magnetometry we have investigated in detail the
magnetization $M$ above the critical temperature $T_c$ in $\rm
Bi_2Sr_2CaCu_2O_{8+\delta}$. In a broad range of temperature $T$ above $T_c$,
we find that $M(T,H)$ is strongly non-linear in the field $H$. We show that as
$T\to T_c$, the susceptibility $\chi(T,H)$ diverges to very large values ($\chi
\to$ -1) if measured in weak $H$. In addition, $M(H)$ displays an anomalous
non-analytic form $M\sim H^{1/\delta}$ in weak fields with a strongly
$T$-dependent exponent $\delta(T)$. These features strongly support the
proposal that, above $T_c$, the pair condensate survives to support significant
London rigidity.

25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
8
The categories of this paper are: hep-ex
0
The categories of this paper are: hep-ph
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
20
The categories of this paper are: acc-phys