Universität zu Köln

Zakutna, D., Matulkova, I., Kentzinger, E., Medlin, R., Su, Y., Nemkovski, K., Disch, Sabrina ORCID: 0000-0002-4565-189X, Vejpravova, J. and Niznansky, D. (2016). Dispersible cobalt chromite nanoparticles: facile synthesis and size driven collapse of magnetism. RSC Adv., 6 (109). S. 107659 - 107669. CAMBRIDGE: ROYAL SOC CHEMISTRY. ISSN 2046-2069

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Abstract

Multiferoic oxides have enormous application potential thanks to the mutually coupled magnetic and dielectric response embedded in a standalone material. Among them, the unique case is the cobalt chromite with spin-induced electric polarization locked to the magnetization direction and propagation vector of the spiral magnetic phase. The nature of the ground state magnetic structure gives rise to complex size dependent magnetic behaviour, which collapses when reaching a critical particle size. In our work, we focused on preparation of standalone cobalt chromite nanoparticles (NPs). We introduced hydrothermal decomposition of cobalt(II)/chromium(III) oleates in a water/ethanol system without need of additional thermal treatment, which lead to stable cobalt chromite nanoparticles with diameter of 3.0(1)-4.2(1) nm and log normal size distribution of 12-16%. The size at the edge of the critical limit was tuned by the reaction temperature reaching typically 240 +/- 10 degrees C. The as-prepared NPs are coated with covalently bonded oleic acid and can be easily dispersed in non-polar solvents, which makes them excellent candidates for custom surface modifications. The NPs were studied using a large number of characterization techniques: powder X-ray diffraction, transmission electron microscopy, small-angle Xray scattering, and vibrational spectroscopies. The impact of the size effect on the magnetic properties was also investigated by temperature and magnetic field dependent magnetization, a.c. susceptibility and diffuse neutron scattering. The onset of the collective glassy state due to the collapse of long range conical magnetic order was observed. The uniform cobalt chromite NPs coated with oleic acid with size of 3-4 nm are excellent prototypes for studying the size effect on magnetic (and feroic) materials, and can be subjected to manifold surface functionalization required for their embedding in smart nanostructures and nanocomposites.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Zakutna, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED Matulkova, I. UNSPECIFIED UNSPECIFIED UNSPECIFIED Kentzinger, E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Medlin, R. UNSPECIFIED UNSPECIFIED UNSPECIFIED Su, Y. UNSPECIFIED UNSPECIFIED UNSPECIFIED Nemkovski, K. UNSPECIFIED UNSPECIFIED UNSPECIFIED Disch, Sabrina UNSPECIFIED orcid.org/0000-0002-4565-189X UNSPECIFIED Vejpravova, J. UNSPECIFIED UNSPECIFIED UNSPECIFIED Niznansky, D. UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-288564
DOI:	10.1039/c6ra21377d
Journal or Publication Title:	RSC Adv.
Volume:	6
Number:	109
Page Range:	S. 107659 - 107669
Date:	2016
Publisher:	ROYAL SOC CHEMISTRY
Place of Publication:	CAMBRIDGE
ISSN:	2046-2069
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Physical Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language HYDROTHERMAL SYNTHESIS; COCR2O4 NANOPARTICLES; SPIN-GLASSES; CATALYSTS; OXIDE; TEMPERATURE; COMBUSTION; STRATEGY; FULCHER; PHASE Multiple languages Chemistry, Multidisciplinary Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/28856