Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Curie temperature and carrier concentration gradients in MBE grown
  GaMnAs layers   We report on detailed investigations of the electronic and magnetic
properties of ferromagnetic GaMnAs layers, which have been fabricated by
low-temperature molecular-beam epitaxy. Superconducting quantum interference
device measurements reveal a decrease of the Curie temperature from the surface
to the GaMnAs/GaAs interface. While high resolution x-ray diffraction clearly
shows a homogeneous Mn distribution, a pronounced decrease of the carrier
concentration from the surface towards the GaMnAs/GaAs interface has been found
by Raman spectroscopy as well as electrochemical capacitance-voltage profiling.
The gradient in Curie temperature seems to be a general feature of GaMnAs
layers grown at low-temperature. Possible explanations are discussed.

18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
8
The categories of this paper are: hep-ex
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
9
The categories of this paper are: nlin
31
The categories of this paper are: ao-sci
16
The categories of this paper are: stat
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom