Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic Phase Transition and Relaxation Effects in LiFePO4   We report the observation of para - antiferromagnetic transition at ~ 50 K in
lithium iron phosphate, LiFePO4 through DC magnetization and M\"ossbauer
spectroscopy. The Ferrous ion Fe2+ (3d6, 5D) in LiFePO4 exhibits relaxation
effects with a relaxation frequency ~1.076 \times 10(rise to 7) s-1 at 300 K.
The temperature dependence of the frequency suggests the origin of the
relaxation is spin-lattice type. The quadrupole splitting at low temperatures
indicates the excited orbital states mix strongly to the orbital doublet ground
state via spin-orbit coupling. Modified molecular field model analysis yields a
saturation value for hyperfine field ~125 kOe. The anomaly in magnetization and
M\"ossbauer parameters below 27 K may be ascribed to contribution of orbital
angular momentum. The high value of the asymmetry parameter ({\eta} ~ 0.8) of
the electric field gradient obtained in the antiferromagnetic regime indicates
a strongly distorted octahedral oxygen neighbourhood for the ferrous sites.

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The categories of this paper are: plasm-ph
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The categories of this paper are: q-fin
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The categories of this paper are: math
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: physics
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The categories of this paper are: astro-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: dg-ga
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The categories of this paper are: gr-qc
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The categories of this paper are: eess