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Tuning coercivity and exchange bias by controlling the interface coupling in bimagnetic core/shell nanoparticles

Abstract

In order to explore an alternative strategy to design exchange-biased magnetic nanostructures, bimagnetic core/shell nanoparticles have been fabricated by a thermal decomposition method and systematically studied as a function of the interface exchange coupling. The nanoparticles are constituted by a ~3 nm antiferromagnetic (AFM) CoO core encapsulated in a ~ 4 nm-thick Co1-xZnxFe2O4 (x = 0-1) ferrimagnetic (FiM) shell. The system presents an enhancement of the coercivity (HC) as compared with its FiM single-phase counterpart and exchange bias fields (HEB). While HC decreases monotonically with the Zn concentration from ~21,5 kOe for x = 0, to ~ 7,1 kOe for x = 1, HEB exhibits a non-monotonous behavior being maximum, HEB ~ 1,4 kOe, for intermediate concentrations. We found that the relation between the AFM anisotropy energy and the exchange coupling energy can be tuned by replacing Co2+ with Zn2+ ions in the shell. As a consequence, the magnetization reversal mechanism of the system is changed from an AFM/FiM rigid-coupling regime to an exchange-biased regime, providing a new approach to tune the magnetic properties and to design novel hybrid nanostructures.

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Publication details

The article was accepted on 10 Jun 2017 and first published on 15 Jun 2017


Article type: Paper
DOI: 10.1039/C7NR03740F
Citation: Nanoscale, 2017, Accepted Manuscript
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    Tuning coercivity and exchange bias by controlling the interface coupling in bimagnetic core/shell nanoparticles

    G. Lavorato, E. Lima, H. E. Troiani, R. Zysler and E. Winkler, Nanoscale, 2017, Accepted Manuscript , DOI: 10.1039/C7NR03740F

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