We aim at combining high coercivity magnetic nanowires in a polymer matrix in a view to fabricate rare--earth free bonded magnets. In particular, our aim is to fabricate anisotropic materials by aligning the wires in the polymer matrix. We have explored the different parameters of the fabrication process in order to produce a material with the best possible magnetic properties. We show that the choice of a proper solvent allows obtaining stable nanowire suspensions. The length and the type of the polymer chains play also an important role. Smaller chains (M w <10000) provide better magnetization results. The magnetic field applied during the casting of the material plays also a role and should be of the order of a fraction of a tesla. The local order of the nanowires in the matrix has been characterized by TEM and Small Angle Neutron Scattering. The correlation between the local order of the wires and the magnetic properties is discussed. Materials with coercivity µ 0 H c up to 0.70 T at room temperature have been obtained.2

The maximum magnetic performance which can be expected from elongated single domain particle based permanent magnets is assessed. The results are derived using micromagnetic calculations to model the behavior of large bundles of aligned nanowires. In particular, we discuss the cases of Co and Fe nanowires and their packing fraction dependence of coercivity, which is the main limiting factor. We show that it is, in principle, feasible to achieve BHmax values close to 300 kJ/m3 in Co nanowires with a packing fraction p = 0.7 and close to 400 kJ/m3 at p = 0.85. The packing fraction limitations are essentially non-existing due to the intrinsic magnetocrystalline anisotropy of Co. On the other hand, if a low anisotropy material such as Fe could be produced in the form of fine, well crystallized wires it could yield a BHmax close to 200 kJ/m3 at an optimum p = 0.7. As the performance of iron nanowires is solely based on shape anisotropy it becomes coercivity limited above p = 0.35.