期刊
NANO LETTERS
卷 13, 期 2, 页码 586-593出版社
AMER CHEMICAL SOC
DOI: 10.1021/nl304115r
关键词
magnetic nanoctystals; cation exchange; exchange bias; nanoheterostructures; ferrites
类别
资金
- Austrian Science Fund FFG via the Austrian Nano Inititative (Project NSI-NanoShape II)
- FWF (project SFB IRON)
- electron microscopy center, at ETH Zurich (EMEZ)
- electron microscopy center, at EMPA
- Swiss SNF (Marie-Heim Vogtlin grant)
- Austrian Academy of Science
- Austrian Science Fund (FWF) [F 2505, F 2507] Funding Source: researchfish
For three types of colloidal magnetic nanocrystals, we demonstrate that postsynthetic cation exchange enables tuning of the nanocrystal's magnetic properties and achieving characteristics not obtainable by conventional synthetic routes. While the cation exchange procedure, performed in solution phase approach, was restricted so far to chalcogenide based semiconductor nanocrystals, here ferrite-based nanocrystals were subjected to a Fe2+ to Co2+ cation exchange procedure. This allows tracing of the compositional modifications by systematic and detailed magnetic characterization. In homogeneous magnetite nanocrystals and in gold/magnetite core shell nanocrystals the cation exchange increases the coercivity field, the remanence magnetization, as well as the superparamagnetic blocking temperature. For core/shell nanoheterostructures a selective doping of either the shell or predominantly of the core with Co2+ is demonstrated. By applying the cation exchange to FeO/CoFe2O4 core/shell nanocrystals the Neel temperature of the core material is increased and exchange-bias effects are enhanced so that vertical shifts of the hysteresis loops are obtained which are superior to those in any other system.
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