Smallest Bimetallic CoPt3 Superparamagnetic Nanoparticles


We present for the first time a nonaqueous sol gel route to produce ultrasmall (<2 nm) magnetic bimetallic CoPt3 nanoparticles (NPs). The one-pot procedure is carried out at low temperature (180 degrees C) using benzyl alcohol, acting as both reducing agent and solvent. The highly monodisperse CoPt3 NPs were investigated with innovative advanced X-ray methods (whole powder pattern modeling), HR-STEM, XPS, and SQUID magnetometry. XPS showed Co was mostly in metallic form, but with a very small amount of CoO on the NP surface. The spherical NPs had an ultrasmall diameter of 1.6 nm and could self-assemble in aligned linear chains, or nanobelts, of single NPs. They are superparamagnetic, with blocking temperature of similar to 20 K and coercivity at 10 K of 27.9 kA m(-1) (similar to 350 Oe). However, there is evidence of a secondmagnetic phase (probably CoO) in the ZFC magnetization curve, which enhances their magnetization values, without significantly affecting their superparamagnetism.



subject category

Chemistry; Science & Technology - Other Topics; Materials Science; Physics


Karmaoui, M; Amaral, JS; Lajaunie, L; Puliyalil, H; Tobaldi, DM; Pullar, RC; Labrincha, JA; Arenal, R; Cvelbar, U

our authors


This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT ref. UID/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement. We acknowledge Fundacao para a Ciencia e a Tecnologia (FCT) for grant SFRH/BPD/74477/2010 (M.K.), Ciencia2008 program and grant SFRH/BPD/97115/2013 (R.C.P.), grant SFRH/BPD/111270/2015 (J.S.A.), M. Ferro for microscopy analysis, which was supported by RNME-Pole University of Aveiro FCT Project REDE/1509/RME/2005, and Prof. Artur Silva for fruitful discussions (University of Aveiro, Portugal). U.C. acknowledges support of Slovenian Research Agency (ARRS) grant no. L2-7667. The STEM and EDS studies were conducted at the Laboratorio de Microscopias Avanzadas, Instituto de Nanociencia de Aragon, Universidad de Zaragoza, Spain. Some of the research leading to these results has received funding from the European Union Seventh Framework Programme under Grant Agreements 312483- ESTEEM2 (Integrated Infrastructure Initiative - I3). RA. gratefully acknowledges the support from the Spanish Ministerio de Economia y Competitividad (FIS2013-46159-C3-3-P) and from the European Union H2020 program ETN project

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