Time-resolved study of surface spin effect on spin-lattice relaxation in Fe3O4 nanocrystals.
The role of surface spins in the relaxation of magnetization in optically excited Fe(3)O(4) nanocrystals has been investigated via time-resolved Faraday rotation measurements. The time scale of the magnetization recovery following the optically induced demagnetization increased from 250 to 350 ps as the size of the nanocrystals increased from 5 to 15 nm. From analysis of the data with a simple model relating the spin-lattice relaxation rate to the average spin-orbit coupling strength of the interior and surface spins, we estimated the relative efficiency of surface in spin-lattice relaxation with respect to the interior spins. Our analysis indicates that, in Fe(3)O(4) nanocrystals passivated with oleic acid, the surface is 3 times more efficient in spin-lattice relaxation than the interior.
Hsia
Chih-Hao
CH
Department of Chemistry, Texas A&M University, College Station, Texas 77842, USA.
Chen
Tai-Yen
TY
Son
Dong Hee
DH