info:eu-repo/semantics/article
Magnetic Interactions and Energy Barrier Enhancement in Core/Shell Bimagnetic Nanoparticles
Fecha
2015-07Registro en:
Lavorato, Gabriel Carlos; Peddis, Davide; Lima, Enio Junior; Troiani, Horacio Esteban; Agostinelli, Elisabetta; et al.; Magnetic Interactions and Energy Barrier Enhancement in Core/Shell Bimagnetic Nanoparticles; American Chemical Society; Journal of Physical Chemistry C; 119; 27; 7-2015; 15755-15762
1932-7447
CONICET Digital
CONICET
Autor
Lavorato, Gabriel Carlos
Peddis, Davide
Lima, Enio Junior
Troiani, Horacio Esteban
Agostinelli, Elisabetta
Fiorani, Dino
Zysler, Roberto Daniel
Winkler, Elin Lilian
Resumen
In this work, we studied the dynamic and static magnetic properties of ZnO-core/CoFe2O4-shell and CoO-core/CoFe2O4-shell nanoparticles. Both systems are formed by a core of ∼4 nm of diameter encapsulated in a shell of ∼2 nm of thickness. The mean blocking temperature changes from 106(7) to 276(5) K when the core is diamagnetic or antiferromagnetic, respectively. Magnetic remanence studies revealed the presence of weak dipolar interparticle interactions, where Hint is approximately -0.1 kOe for ZnO/CoFe2O4 and -0.9 kOe for CoO/CoFe2O4, playing a minor role in the magnetic behavior of the materials. Relaxation experiments provided evidence that the magnetization reversal process of CoFe2O4 is strongly dependent on the magnetic order of the core. At 10 K, activation volumes of ∼46(6) and ∼69(5) nm3 were found for CoO/CoFe2O4 and ZnO/CoFe2O4 nanoparticles, respectively, corresponding to one-third and one-fifth of the total shell volume. While the magnetic behavior of ZnO/CoFe2O4 nanoparticles is strongly affected by the surface disorder, the exchange coupling at the CoO/CoFe2O4 interface rules the magnetization reversal and the nanoparticles' thermal stability by inducing a larger energy barrier and promoting smaller switching volume.