Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A study of crossover from 3D ferrimagnetic Bulk $NiCr_{2}O_{4}$ compound
  into 2D spin-glass like nanophase   In this report, the magnetic behaviour of $NiCr_{2}O_{4}$ bulk and
nanoparticle samples under different applied magnetic field has been
investigated extensively. Nanoparticles of $NiCr_{2}O_{4}$ were obtained by
mechanical milling of polycrystalline powder prepared by polyol method. FC-ZFC
measurement of bulk at different applied magnetic field has revealed the
existence of a ferrimagnetic transition around 66K followed by an
antiferromagnetic transition close to 30K. However, its nano counterpart has
shown remarkable change in magnetic properties - a suppression of ferrimagnetic
transition accompanied by strengthening low temperature magnetic phase and
observation of a new transition at 90K ($T_P$), which is weakly magnetic in
nature. The frequency dependent ac susceptibility data of nanoparticle have
been fitted to the well known de Almedia-Thouless equation and a $H^{2/3}$
dependence of the low temperature peak is observed with a resulting zero field
freezing temperature ($T_f^0$) equal to 10.1K. Further, the dynamical behaviour
near freezing temperature has been analysed in terms of critical behaviour and
the obtained fitted parameters values being as $\tau_0$(relaxation time
constant) = $3.6 X 10^{-6}s$, $T_f^0=8.7$K and $z\nu = 11.1$. Moreover,
Vogel-Fulcher law has been used to understand the nature of freezing transition
and the parameter after fitting are obtained as $E_a/k_B = 58.9$K, $\tau_0 =
5.22 \times 10^{-8}$ and $T_0 = 8.03$K. Finally, the spin-glass phase is
concluded. Moreover, in contrast to bulk, the $H^{2/3}$ dependence of freezing
temperature of nanoparticle sample (75h) does support the 2D surface like spin
glass nature.

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The categories of this paper are: econ
20
The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: hep-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: comp-gas
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The categories of this paper are: atom-ph
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The categories of this paper are: cs
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The categories of this paper are: hep-th
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The categories of this paper are: alg-geom
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The categories of this paper are: quant-ph
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The categories of this paper are: mtrl-th