Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Interplay between Fe and Nd magnetism in NdFeAsO single crystals   The structural and magnetic phase transitions have been studied on NdFeAsO
single crystals by neutron and x-ray diffraction complemented by resistivity
and specific heat measurements. Two low-temperature phase transitions have been
observed in addition to the tetragonal-to-orthorhombic transition at T_S = 142
K and the onset of antiferromagnetic (AFM) Fe order below T_N = 137 K. The Fe
moments order AFM in the well-known stripe-like structure in the (ab) plane,
but change from AFM to ferromagnetic (FM) arrangement along the c direction
below T* = 15 K accompanied by the onset of Nd AFM order below T_Nd = 6 K with
this same AFM configuration. The iron magnetic order-order transition in
NdFeAsO accentuates the Nd-Fe interaction and the delicate balance of c-axis
exchange couplings that results in AFM in LaFeAsO and FM in CeFeAsO and
PrFeAsO.

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The categories of this paper are: q-alg
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The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
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The categories of this paper are: q-fin
12
The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: comp-gas
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The categories of this paper are: funct-an
11
The categories of this paper are: hep-lat
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The categories of this paper are: patt-sol
33
The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: ao-sci