Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ferromagnetic order in aged Co-doped TiO2 anatase nanopowders   Oxide based diluted magnetic semiconductor (DMS) materials have been a
subject of increasing interest due to reports of room temperature
ferromagnetism in several systems and their potential use in the development of
spintronic devices. However, concerns on the stability of the magnetic
properties of different DMS systems have been raised. Their magnetic moment is
often unstable, vanishing with a characteristic decay time of weeks or months,
which precludes the development of real applications. This paper reports on the
ferromagnetic properties of two-year-aged Ti1-xCoxO2-{\delta} reduced anatase
nanopowders with different Co contents (0.03<x<0.10). Aged samples retain
rather high values of magnetization, remanence and coercivity which provide
strong evidence for a quite preserved long-range ferromagnetic order. In what
concern Co segregation, some degree of metastability of the diluted Co doped
anatase structure could be inferred in the case of the sample with the higher
Co content.

32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics
27
The categories of this paper are: comp-gas
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat