Synthesis, structure and magnetic properties of multipod-shaped cobalt ferrite nanocrystals


We applied a general non-aqueous route for the formation of mono-, bi-, tri-, tetra, hexapod and multipod magnetic spinel ferrite metal oxide (CoFe2O4) nanocrystals. The magnetic CoFe2O4 nanocrystals were characterized by X-ray diffraction, high-resolution transmission electron microscopy, Raman spectroscopy, magnetometry and Mossbauer spectroscopy, to understand their structure and magnetic properties. These CoFe2O4 nanoparticles have the smallest particle size reported ever, with a mean diameter of similar to 3 nm. The coercivity was found to be larger compared to that reported in the literature for spherical particles. Mossbauer spectroscopy indicated a magnetic transition above room temperature, where 20% of the Fe ions transit to a paramagnetic state, around 400 K. From the thermal dependence of magnetic parameters, the blocking temperature was estimated to be around 425 K. These studies indicate that our CoFe2O4 nanocrystals are different from their cubic/spherical counterparts, which generally display a single domain character. These CoFe2O4 nanocrystals display a strong shape anisotropy dependent magnetic property.






Hennous, M; Ramana, EV; Tobaldi, DM; Costa, BFO; Valente, MA; Labrincha, J; Karmaoui, M

nossos autores


Mohamed Karmaoui thanks Fundacao para a Ciencia e a Tecnologia (FCT) for Grant no. SFRH/BPD/74477/2010. This work was developed in the scope of the project CICECO-Aveiro Institute of Materials (Ref. FCT UID/CTM/50011/2013). This work was developed within funds from the project CICECO-Aveiro Institute of Materials, FCT Ref. ID/CTM/50011/2019, financed by national funds through the FCT/MCTES and when appropriate co-financed by FEDER under the PT2020 Partnership. Venkata Ramana would like to acknowledge the financial support from the FCT, Portugal (SFRH/BPD/75582/2010) and COMPETE 2020, national funds (UID/CTM/50025/2013). Some of the research leading to these results has received funding from the European Union Seventh Framework Program under Grant Agreement 312483 - ESTEEM2 (Integrated Infrastructure Initiative - I3). David Maria Tobaldi is grateful to Portuguese national funds (OE), through FCT, I.P., in the scope of the framework contract foreseen in the numbers 4, 5 and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19. This work was also supported by funds from FEDER (Programa Operacional Factores de Competitividade COMPETE) and from FCT-Fundacao para a Ciencia e a Tecnologia under the Project No. UID/FIS/04564/2016.

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