Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for a transition from a bulk Meissner-state to a spontaneous
  vortex phase in RuSr$_2$GdCu$_2$O$_8$ from DC magnetisation measurements   From magnetisation measurements we provide evidence that the ferromagnetic
superconductor RuSr$_{2}$GdCu$_{2}$O$_{8}$ with \QTR{it}{T}$_{c}$=45 K and
\QTR{it}{T}$_{M}$=137 K exhibits a sizeable diamagnetic signal at low
temperature (\QTR{it}{T}<\QTR{it}{T}$^{\QTR{it}{ms}}$=30 K) and low magnetic
field (\QTR{it}{H}$^{ext}$<30 Oe), corresponding to a bulk Meissner-phase. At
intermediate temperatures,
\QTR{it}{T}$^{\QTR{it}{ms}}$<\QTR{it}{T}<\QTR{it}{T}$_{c}$, a spontaneous
vortex phase forms which is characterized by unique thermal hysteresis effects.
We argue that a recent negative report [C.W. Chu et al., cond-mat/9910056]
regarding the Meissner-effect in Ru-1212 can be explained by impurity
scattering or grain size effects.

35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
32
The categories of this paper are: atom-ph
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
2
The categories of this paper are: math