Nanocrystalline SmCo5 magnets with laminated structure and increased electrical resistivity

Abstract

Magnetically isotropic Sm–Co permanent magnets with anisotropic electrical conductivity were produced by hot-pressing SmCo5 ultrathin flakes with or without insulating additions of mica, MoS2, CaF2, and B2O3. The laminated structures of the magnets were assured by the natural packing of the flakes in the die. In the additive-free magnets, the resistivity is increased due to oxidized flake boundaries. Additives with platelet-shaped particles (mica, MoS2) and especially those with low-melting temperature (B2O3) form more continuous insulating layers. On the other hand, the CaF2 additive does not react with the magnetic Sm–Co phase. The characteristic values of the maximum energy product and electrical resistivity, measured in orthogonal directions, were 9.7 MG Oe and 130 μΩ cm for the additive-free magnet, 5.7 MG Oe and 640 μΩ cm for the magnet made with 2 wt. % B2O3 and 5.7 MG Oe and 330 μΩ cm for the magnet made with 10 wt. % CaF2.