Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic spin excitations in diluted ferromagnetic systems: the case of
  $Ga_{1-x}Mn_{x}As$   We propose a theory which allow to calculate the magnetic excitation spectrum
in diluted ferromagnetic systems. The approach is rather general and based on
the Self-Consistent local Random Phase Approximation in which disorder
(dilution) and thermal fluctuations are properly treated. To illustrate its
reliability and accuracy we calculate the magnetic excitation in the diluted
III-V magnetic semiconductor $Ga_{1-x}Mn_{x}As$. It is shown that dilution has
a drastic effect on the excitation spectrum, indeed well defined magnon
excitations exist only in a small region of the Brillouin zone centered around
the $\Gamma$ point. We also calculate the spin stiffness in optimally annealed
sample as a function of $Mn^{2+}$ concentration. A comparison to available
measurements is done. We find a very good agreement for both the Curie
temperature and the spin stiffness measured in well annealed samples and
provide a plausible explanation for the very small values measured in as grown
samples.

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The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
19
The categories of this paper are: eess
2
The categories of this paper are: math
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
15
The categories of this paper are: nucl-ex