Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Superspin Glass Mediated Giant Spontaneous Exchange Bias in a
  Nanocomposite of BiFeO$_3$-Bi$_2$Fe$_4$O$_9$   We observe an enormous $\textit{spontaneous}$ exchange bias ($\sim$300-600
Oe) - measured in an unmagnetized state following zero-field cooling - in a
nanocomposite of BiFeO$_3$ ($\sim$94%)-Bi$_2$Fe$_4$O$_9$ ($\sim$6%) over a
temperature range 5-300 K. Depending on the path followed in tracing the
hysteresis loop - positive (p) or negative (n) - as well as the maximum field
applied, the exchange bias ($H_E$) varies significantly with $\mid-H_{Ep}\mid$
$>$ $\mid H_{En}\mid$. The temperature dependence of $H_E$ is nonmonotonic. It
increases, initially, till $\sim$150 K and then decreases as the blocking
temperature $T_B$ is approched. All these rich features appear to be
originating from the spontaneous symmetry breaking and consequent onset of
unidirectional anisotropy driven by "superinteraction bias coupling" between
ferromagnetic core of Bi$_2$Fe$_4$O$_9$ (of average size $\sim$19 nm) and
canted antiferromagnetic structure of BiFeO$_3$ (of average size $\sim$112 nm)
via superspin glass moments at the shell.

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The categories of this paper are: nlin
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-ex
2
The categories of this paper are: math
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The categories of this paper are: bayes-an
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The categories of this paper are: chao-dyn
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The categories of this paper are: stat
31
The categories of this paper are: ao-sci
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The categories of this paper are: astro-ph
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The categories of this paper are: q-alg
1
The categories of this paper are: cs
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The categories of this paper are: eess
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: adap-org
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The categories of this paper are: atom-ph