The effect of Nd8Cu2 alloy on the microstructure and magnetic properties of (Nd, MM)-Fe-B sintered magnets

•Nd8Cu2 alloy powders have been added into the (MM0.3Nd0.7)-Fe-B Multi-main-phase magnet.•With the addition of 5 wt% Nd8Cu2 alloy powders, the Hcj of the magnet increase to 10.99 kOe from 7.01 kOe.•The Nd-rich (Nd, MM)-Fe-B hard magnetic shell layers have formed on the surface of the MM-Fe-B grains.•The phase of NdCu2 with the structure of Orthorhombic is found at the grain boundary.