Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Optical evidence for a spin-filter effect in the charge transport of
  $Eu_{0.6}Ca_{0.4}B_{6}$   We have measured the optical reflectivity $R(\omega)$ of
$Eu_{0.6}Ca_{0.4}B_{6}$ as a function of temperature between 1.5 and 300 $K$
and in external magnetic fields up to 7 $T$. The slope at the onset of the
plasma edge feature in $R(\omega)$ increases with decreasing temperature and
increasing field but the plasma edge itself does not exhibit the remarkable
blue shift that is observed in the binary compound $EuB_{6}$. The analysis of
the magnetic field dependence of the low temperature optical conductivity
spectrum confirms the previously observed exponential decrease of the
electrical resistivity upon increasing, field-induced bulk magnetization at
constant temperature. In addition, the individual exponential magnetization
dependences of the plasma frequency and scattering rate are extracted from the
optical data.

23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
27
The categories of this paper are: comp-gas
31
The categories of this paper are: ao-sci
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
2
The categories of this paper are: math
16
The categories of this paper are: stat
0
The categories of this paper are: hep-ph
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol