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@ARTICLE{Galivarapu:828002,
author = {Galivarapu, Jagadish K. and Kumar, D. and Banerjee, A. and
Rath, Chandana},
title = {{M}agnetic {T}ransitions in {C}hemically {S}ynthesized
{N}anoparticles of {C}o{C}r$_{2}$ {O}$_{4}$},
journal = {IEEE transactions on magnetics},
volume = {52},
number = {8},
issn = {1941-0069},
address = {New York, NY},
publisher = {IEEE},
reportid = {FZJ-2017-02024},
pages = {1 - 6},
year = {2016},
abstract = {Bulk CoCr2O4 undergoes a transition from paramagnetic to
long-range ferrimagnetic phase at Ts (94 K) to a long-range
and/or short-range spiral order at Ts (~24 K), and finally
shows a lock-in-transition below 15 K. The spiral component
induces an electric polarization and also a spontaneous
magnetization for which it is said to be multiferroic.
Reducing the size of a CoCr2O4 multiferroic material to ~50
nm by a coprecipitation method, we obtain a pure cubic phase
with space group, Fd3m and lattice parameter (8.334 ±
0.003°A). A rich sequence of magnetic transitions are
examined by measuring temperature and field-dependent
magnetization and diffused neutron scattering (DNS) using
polarized neutron at different temperatures. While
paramagnetic to ferrimagnetic transition is enhanced from 97
K in bulk to 99 K at 0.5 kOe field, followed by a decrease
in lock-in-transition (TL) from 15 K in bulk to 8 K, spiral
ordering temperature does not show a significant change. A
strong disagreement between paramagnetic moment obtained
from the fitting of χ-1 = (T/C) + (1/χo) - (b/T - θ) and
ferrimagnetic moment obtained from the M versus H loop taken
at 2 K, nonsaturated magnetization at 50-100 kOe field, two
order of magnitude higher coercivity (Hc), and splitting of
ac susceptibly confirm the core-shell structure of the
particles. Furthermore, a magnetic scattering analysis
clearly shows that while the paramagnetic to ferrimagnetic
transition is continuous, the spiral ordering is sharp,
short range, and commensurate in contrast to incommensurate
spiral order observed single crystal of CoCr2O4.},
cin = {JCNS (München) ; Jülich Centre for Neutron Science JCNS
(München) ; JCNS-FRM-II / JCNS-2},
ddc = {620},
cid = {I:(DE-Juel1)JCNS-FRM-II-20110218 /
I:(DE-Juel1)JCNS-2-20110106},
pnm = {6G15 - FRM II / MLZ (POF3-6G15) / 6G4 - Jülich Centre for
Neutron Research (JCNS) (POF3-623)},
pid = {G:(DE-HGF)POF3-6G15 / G:(DE-HGF)POF3-6G4},
experiment = {EXP:(DE-MLZ)DNS-20140101},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000380359200013},
doi = {10.1109/TMAG.2016.2537794},
url = {https://juser.fz-juelich.de/record/828002},
}