Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Unconventional Superconductivity and Nearly Ferromagnetic Spin
  Fluctuations in Na$_x$CoO$_2$$\cdot y$H$_2$O   Co NQR studies were performed in recently discovered superconductor
Na$_x$CoO$_2$$\cdot y$H$_2$O to investigate physical properties in the
superconducting (SC) and normal states. Two samples from the same Na$_x$CoO$_2$
were examined, SC bilayer-hydrate sample with $T_c \sim 4.7$ K and non-SC
monolayer-hydrate sample. From the measurement of nuclear-spin lattice
relaxation rate $1/T_1$ in the SC sample, it was found that the coherence peak
is absent just below $T_c$ and that $1/T_1$ is proportional to temperature far
below $T_c$. These results, which are in qualitatively agreement with the
previous result by Fujimoto {\it et al.}, suggest strongly that unconventional
superconductivity is realized in this compound. In the normal state, $1/T_1T$
of the SC sample shows gradual increase below 100K down to $T_c$, whereas
$1/T_1T$ of the non-SC sample shows the Korringa behavior in this temperature
range. From the comparison between $1/T_1T$ and $\chi_{\rm bulk}$ in the SC
sample, the increase of $1/T_1T$ is attributed to nearly ferromagnetic
fluctuations. These remarkable findings suggest that the SC sample possesses
nearly ferromagnetic fluctuations, which are possibly related with the
unconventional superconductivity in this compound. The implication of this
finding is discussed.

31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
22
The categories of this paper are: chao-dyn
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
19
The categories of this paper are: eess
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
36
The categories of this paper are: cmp-lg
24
The categories of this paper are: dg-ga
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
17
The categories of this paper are: q-fin