Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Surface spin-flop and discommensuration transitions in antiferromagnets   Phase diagrams as a function of anisotropy $D$ and magnetic field $H$ are
obtained for discommensurations and surface states for an antiferromagnet in
which $H$ is parallel to the easy axis, by modeling it using the ground states
of a one-dimensional chain of classical XY spins. A surface spin-flop phase
exists for all $D$, but the interval in $H$ over which it is stable becomes
extremely small as $D$ goes to zero. First-order transitions, separating
different surface states and ending in critical points, exist inside the
surface spin-flop region. They accumulate at a field $H'$ (depending on $D$)
significantly less than the value $H_{SF}$ for a bulk spin-flop transition. For
$H' < H < H_{SF}$ there is no surface spin-flop phase in the strict sense;
instead, the surface restructures by, in effect, producing a discommensuration
infinitely far away in the bulk. The results are used to explain in detail the
phase transitions occurring in systems consisting of a finite, even number of
layers.

12
The categories of this paper are: nucl-th
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The categories of this paper are: stat
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
29
The categories of this paper are: funct-an
24
The categories of this paper are: dg-ga
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
28
The categories of this paper are: alg-geom
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The categories of this paper are: eess