Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A Magnetic Transition Probed by the Ce Ion in Square-Lattice
  Antiferromagnet CeMnAsO   We examined the magnetic properties of the square-lattice antiferromagnets
CeMnAsO and LaMnAsO and their solid solutions La1-xCexMnAsO by resistivity,
magnetic susceptibility, and heat capacity measurements below room temperature.
A first-order phase transition is observed at 34.1 K, below which the
ground-state doublet of the Ce ion splits by 3.53 meV. It is likely that Mn
moments already ordered above room temperature are reoriented at the
transition, as reported for related compounds, such as NdMnAsO and PrMnSbO.
This transition generates a large internal magnetic field at the Ce site in
spite of the fact that simple Heisenberg interactions should be cancelled out
at the Ce site owing to geometrical frustration. The transition takes place at
nearly the same temperature with the substitution of La for Ce up to 90%. The
Ce moment does not undergo long-range order by itself, but is parasitically
induced at the transition, serving as a good probe for detecting the magnetism
of Mn spins in a square lattice.

2
The categories of this paper are: math
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
21
The categories of this paper are: adap-org
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin