Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic ordering induced by interladder coupling in the spin-1/2
  Heisenberg two-leg ladder antiferromagnet C$_9$H$_{18}$N$_2$CuBr$_4$   We present specific-heat and neutron-scattering results for the \emph{S}=1/2
quantum antiferromagnet (dimethylammonium)(3,5-dimethylpyridinium)CuBr$_4$. The
material orders magnetically at \emph{T}$_N$=1.99(2)\,K, and magnetic
excitations are accompanied by an energy gap of 0.30(2) meV due to spin
anisotropy. The system is best described as coupled two-leg spin-1/2 ladders
with the leg exchange $J_{\rm leg}$=0.60(2)~meV, rung exchange $J_{\rm
rung}$=0.64(9)~meV, interladder exchange $J_{\rm int}$=0.19(2)~meV, and an
interaction-anisotropy parameter $\lambda$=0.93(2), according to inelastic
neutron-scattering measurements. In contrast to most spin ladders reported to
date, the material is a rare example in which the interladder coupling is very
near the critical value required to drive the system to a N\'eel-ordered phase
without an assistance of a magnetic field.

25
The categories of this paper are: patt-sol
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
21
The categories of this paper are: adap-org