Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Terahertz and Infrared Studies of Antiferroelectric Phase Transition in
  Multiferroic Bi_0.85Nd_0.15FeO_3   High-frequency dielectric studies of Bi_0.85Nd_0.15FeO_3 ceramics performed
betweeen 100 and 900 K reveal hardening of most polar phonons on cooling below
antiferroelectric phase transition, which occurs near 600 K. Moreover, a strong
THz dielectric relaxation is seen in paraelectric phase. Its relaxation
frequency softens on cooling towards Tc ~ 600 K, its dielectric strength
simultaneously decreases and finaly the relaxation disappears from the spectra
below 450 K. Both phonon and dielectric relaxation behavior is responsible for
a decrease in the dielectric permittivity at the antiferroelectric phase
transition. Origin of unusual strong THz dielectric relaxation in paraelectric
phase is discussed. Bi_0.85Nd_0.15FeO_3 structrure lies on the phase boundary
between polar rhombohedral and non-polar orthorhombic phase and owing to this
the polarization rotation and polarization extension can enhance the
piezoelectric response of this system. Similarities and discrepancies with
lead-based piezoelectric perovskites, exhibiting morphotrophic phase boundary
between two ferroelectric phases, are discussed.

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The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: plasm-ph
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The categories of this paper are: math
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: cs
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The categories of this paper are: physics
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The categories of this paper are: q-alg
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th