Assembly and Alignment of Nano-objects for Advanced Magnetic Materials

摘要

Exchange-coupled nanocomposites are promising for the fabrication of next-generation permanent-magnets with improved energy products, but the easy-axis alignment of the hard phase and producing appropriate nanostructure are key issues. In the present study, we investigate the structural and magnetic properties of the easy-axis aligned RCo_5:Fe-Co (R = Y, Sm) and L1_0-FePt:Fe-rich fcc-Fe(Pt) nanocomposites produced by cluster-deposition and template-assisted sputtering methods, respectively. A large inclusion of soft Fe-Co phase of about 30 vol. % improves the magnetic polarization J_s of SmCo_5:Fe-Co to 12.7 kG at 300 K, but the coercivity H_c is substantially reduced to 0.6 kOe due to the propagation of domain walls. On the other hand, the presence of a thin non-magnetic layer around each nanocomposite grain in L1_0-FePt:fcc-Fe(Pt) inhibits domain expansion by pinning of domain walls and maintains H_c as high as 30-40 kOe and a high (BH)_(max) of more than 50 MGOe with inclusion of soft phases.