We have observed a glassy dynamics of the exchange bias properties in a granular system composed of Fe nanoparticles dispersed in a structurally and magnetically disordered (cluster glass-like) Fe oxide matrix. The exchange field, measured at T = 5 K, increases with increasing the time tw spent at T = 50 K, after applying the cooling field. During tw, the oxide phase evolves towards a lower energy configuration, resulting in a stronger interface exchange coupling with the Fe particle moments. Monte Carlo simulations on core/shell nanoparticles reproduce such aging effect, provided that a shell random anisotropy is assumed.
D. Fiorani, L. Del Bianco, A.M. Testa, K.N. Trohidou (2006). Glassy dynamics in the exchange bias properties of the Fe/FeOxide nanogranular system. PHYSICAL REVIEW. B, CONDENSED MATTER AND MATERIALS PHYSICS, 73, 092403-092403-4 [10.1103/PhysRevB.73.092403].
Glassy dynamics in the exchange bias properties of the Fe/FeOxide nanogranular system
DEL BIANCO, LUCIA;
2006
Abstract
We have observed a glassy dynamics of the exchange bias properties in a granular system composed of Fe nanoparticles dispersed in a structurally and magnetically disordered (cluster glass-like) Fe oxide matrix. The exchange field, measured at T = 5 K, increases with increasing the time tw spent at T = 50 K, after applying the cooling field. During tw, the oxide phase evolves towards a lower energy configuration, resulting in a stronger interface exchange coupling with the Fe particle moments. Monte Carlo simulations on core/shell nanoparticles reproduce such aging effect, provided that a shell random anisotropy is assumed.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
