Structure and Magnetic Properties of Low Neodymium Magnets Containing Minor Addition of Molybdenum

Rapidly solidified nanocomposite Nd₉Fe_77-xB₁₄Mo_x alloys, consisting of magnetic Nd₂Fe₁₄B phase and soft magnetic phases, were investigated. The effect of the molybdenum addition on the structure and magnetic properties was studied. It was found that 3-4 at% Mo addition leads to a substantial increase of the coercivity and maximum energy product maintaining the remanence to be almost unchanged. The highest properties J_r = 0.755 T,_J H_c = 1030 kA/m,(BH)_max= 87 kJ/m³ were obtained for the Nd₉Fe₇₃B₁₄Mo₄ alloy. This effect we ascribe to the formation of a fine and homogeneous grain structure and a change of the phase constitution in the Mo-containing alloys. The initial magnetization curve indicates a change of the coercivity mechanisms, giving rise to the pinning of domain walls, which is caused by a reduction of the crystallite size.