Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Pressure-induced phase transitions in the multiferroic perovskite BiFeO3
  studied by far-infrared micro-spectroscopy   We present the results of pressure-dependent far-infrared reflectivity
measurements on the multiferroic perovskite BiFeO3 at room temperature. The
observed behavior of the infrared-active phonon modes as a funtion of pressure
clearly reveals two structural phase transitions around 3.0 and 7.5 GPa,
supporting the results of recent Raman and x-ray diffraction studies under
pressure. Based on the pressure-dependent frequency shifts of the
infrared-active phonon modes we discuss the possible character of the phase
transitions.

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The categories of this paper are: astro-ph
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The categories of this paper are: math
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The categories of this paper are: nucl-th
18
The categories of this paper are: econ
36
The categories of this paper are: cmp-lg
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The categories of this paper are: quant-ph
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The categories of this paper are: stat
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
31
The categories of this paper are: ao-sci