Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Crystal structures, magnetic and superconducting properties of the
  RuSr_2NdCu_2O_x and RuSr_2GdCu_2O_y compounds   We report the magnetization and the susceptibility measurements of the
RuSr_2GdCu_2O_y and RuSr_2NdCu_2O_x perovskite materials. We find that
RuSr_2GdCu_2O_y compound exhibits a magnetic transition at Tn=135 K followed by
a superconducting one with an onset Tc=35 K. Samples of RuSr_2NdCu_2O_x
material have shown neither superconductivity nor magnetic transition. XRD
measurements show that in RuSr_2NdCu_2O_x the Nd ions tend to substitute to Sr
ions in very high percentages. The relevance of this phenomenon on the absence
of superconductivity in RuSr_2NdCu_2O_x is discussed.

17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
15
The categories of this paper are: nucl-ex
36
The categories of this paper are: cmp-lg
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con