Tuning the magnetic properties of metal oxide nanocrystal heterostructures by cation exchange.
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 Fe(2+) to Co(2+) 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 Co(2+) is demonstrated. By applying the cation exchange to FeO/CoFe(2)O(4) core/shell nanocrystals the Neél 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.
Institute of Semiconductor and Solid State Physics, University Linz, Altenbergerstraße 69, 4040 Linz, Austria.
Mykhailo
M
Sytnyk
Raimund
R
Kirchschlager
Maryna I
MI
Bodnarchuk
Daniel
D
Primetzhofer
Dominik
D
Kriegner
Herbert
H
Enser
Julian
J
Stangl
Peter
P
Bauer
Michael
M
Voith
Achim Walter
AW
Hassel
Frank
F
Krumeich
Frank
F
Ludwig
Arno
A
Meingast
Gerald
G
Kothleitner
Maksym V
MV
Kovalenko
Wolfgang
W
Heiss
D002412:Cations / Q000737:chemistry; D003035:Cobalt / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D060526:Magnetic Fields; D049329:Nanostructures / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D013696:Temperature
D002412:Cations; D005290:Ferric Compounds; D010087:Oxides; C000499:ferric oxide; D003035:Cobalt; C060728:cobalt oxide