Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for s-wave pairing from measurement on lower critical field in
  $MgCNi_3$   Magnetization measurements in the low field region have been carefully
performed on a well-shaped cylindrical and an ellipsoidal sample of
superconductor $MgCNi_3$. Data from both samples show almost the same results.
The lower critical field $H_{c1}$ and the London penetration depth $\lambda$
are thus derived. It is found that the result of normalized superfluid density
$\lambda^2(0)/\lambda^2(T)$ of $MgCNi_3$ can be well described by BCS
prediction with the expectation for an isotropic s-wave superconductivity.

24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
3
The categories of this paper are: physics
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
37
The categories of this paper are: supr-con
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph