Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetization and magnon excitation energies of the magnetic
  semiconductors EuTe and EuO on the basis of the renormalized spin wave theory   We present analytic expressions for the temperature dependent magnetization
and magnon dispersion relation of the antiferromagnetic (AFM) EuTe and the
ferromagnetic (FM) EuO. These bulk semiconductors represent concentrated spin
systems for which the interaction between magnons has to be taken into account.
We do this using the renormalized spin wave theory. A higher order Green's
function according to Tjablikov is used for their description. As a result, we
obtain a modified Bloch- T3/2 law, for low temperatures and high magnetic
fields. A full analytic expression is given for the sublattice magnetization of
the AFM EuTe (B0=0), with a N\'eel temperature of TN = 9.81 K. The
magnetization curves {\sigma}N(T) of EuO (for 0 \leq T \leq 0.68TC) and
{\sigma}R(T) (for 0.82TC < T < TC) agree well with experiment. The spin wave
excitation energy perfectly matches experimental data from inelastic neutron
scattering. In the case of EuTe the magnon excitation energies exhibit a
characteristic maximum. For q = 0, an energy gap Eg occurs in the spin wave
spectrum, a consequence of the AFM exchange interaction J2(T). Such energy gaps
exist in the spectrum of magnon excitation energies only in systems with AFM
interactions.

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The categories of this paper are: funct-an
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The categories of this paper are: econ
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The categories of this paper are: ao-sci
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: plasm-ph
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The categories of this paper are: supr-con
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: nlin
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: physics
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The categories of this paper are: stat
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The categories of this paper are: cs
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The categories of this paper are: gr-qc