Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superconductivity and magnetism in RbxFe2-ySe2: Impact of thermal
  treatment on mesoscopic phase separation   An extended study of the superconducting and normal-state properties of
various as-grown and post-annealed RbxFe2-ySe2 single crystals is presented.
Magnetization experiments evidence that annealing of RbxFe2-ySe2 at 413 K, well
below the onset of phase separation Tp=489 K, neither changes the magnetic nor
the superconducting properties of the crystals. In addition, annealing at 563
K, well above Tp, suppresses the superconducting transition temperature Tc and
leads to an increase of the antiferromagnetic susceptibility accompanied by the
creation of ferromagnetic impurity phases, which are developing with annealing
time. However, annealing at T=488K=Tp increases Tc up to 33.3 K, sharpens the
superconducting transition, increases the lower critical field, and strengthens
the screening efficiency of the applied magnetic field. Resistivity
measurements of the as-grown and optimally annealed samples reveal an increase
of the upper critical field along both crystallographic directions as well as
its anisotropy. Muon spin rotation and scanning transmission electron
microscopy experiments suggest the coexistence of two phases below Tp: a
magnetic majority phase of Rb2Fe4Se5 and a non-magnetic minority phase of
Rb0.5Fe2Se2. Both microscopic techniques indicate that annealing the specimens
just at Tp does not affect the volume fraction of the two phases, although the
magnetic field distribution in the samples changes substantially. This suggests
that the microstructure of the sample, caused by mesoscopic phase separation,
is modified by annealing just at Tp, leading to an improvement of the
superconducting properties of RbxFe2-ySe2 and an enhancement of Tc.

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The categories of this paper are: astro-ph
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The categories of this paper are: math-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: hep-ex
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: atom-ph
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The categories of this paper are: math
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The categories of this paper are: hep-lat
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin
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The categories of this paper are: adap-org
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The categories of this paper are: nlin