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

Rapidly solidified nanocomposite Nd
₉
Fe
_77-x
B
₁₄
Mo
_x
alloys, consisting of magnetic Nd
₂
Fe
₁₄
B 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/m
³
were obtained for the Nd
₉
Fe
₇₃
B
₁₄
Mo
₄
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.