Investigation of hard magnetic properties of nanocomposite Fe-Pt magnets by micromagnetic simulation

Micromagnetic finite element method is used to simulate magnetic properties of FePt/Fe3Pt exchange-coupled nanocomposites. Numerical results show that the maximum energy product (BH)(max) about 34.6 MGOe can be obtained for the 3-nm-scale isotropic magnets with the volume fraction of soft Fe3Pt phase v(s)=15%. The appearance of touched soft grains causes the decrease of reduced remanence m(r) when v(s) exceeds 20%. Coercivity decreases with the simultaneous decrease of D-s and D-h, where D-s and D-h are the grain sizes of soft and hard phases, respectively. Only under the prerequisite of sufficiently large D-h, the coercivity can be improved remarkably by decreasing D-s below twice the domain wall width of hard phase. (C) 2004 American Institute of Physics.