High energy product in mechanically alloyed ThMn12-type compound with exchange coupling effect

The phase formations and the magnetic properties of the mechanically milled NdFe11−yCoyMo1Nx (y=0, 0.5, 1, 1.6, 2.2) compounds have been studied. A relatively high remanence to saturation magnetization ratio of 0.6-0.7 and a high coercivity up to 9.5 kOe were achieved for these nitrides. It is found that the substitution of Co for Fe plays a key role in the grain growth and the grain distribution of α-Fe. The remanences and the coercivities of these compounds increase with the Co content up to y⩽1.6. These compounds show a significant remanence enhancement which can be attributed to the magnetic exchange coupling between Nd(Fe,Mo)12Nx and the α-Fe(Co) grains. The maximum energy product (BH)max of about 8.3 MG Oe is obtained for NdFe10Co1Mo1Nx with a Hc of ∼9.5kOe and a Mr of ∼78emu/g.