Author/Authors :
Hwang، نويسنده , , Yosun and Angappane، نويسنده , , S. and Park، نويسنده , , Jongnam Park، نويسنده , , Kwangjin and Hyeon، نويسنده , , T. and Park، نويسنده , , Je-Geun Park، نويسنده ,
Abstract :
We have carried out systematic studies on well-characterized monodisperse Fe3O4/γ-Fe2O3 core/shell nanoparticles of 2–30 nm having a very narrow size distribution and possessing a uniquely mono-layer of surface γ-Fe2O3. This unique core-shell structure, probably having a disordered magnetic surface state, leads us to three key observations of unusual magnetic properties: i) a very large magnetic exchange anisotropy reaching over 7 × 106 erg/cm3 for the smaller particles, ii) exchange bias behavior in the magnetization data of the core/shell Fe3O4/γ-Fe2O3 nanoparticles, and iii) the temperature dependence of the coercive field following an unusual exponential behavior.
