Effect of Sn on magnetic properties of sintered NdFeB

Magnetic properties of NdFeB magnets with addition of various amounts of Sn by two powder method were studied. It is showed that all properties of NdFeB are degraded by adding Sn. However, coercivity of NdDyFeAlB is improved with addition of Sn when magnet has been annealed at proper temperature. However, the coercivity is decreased by annealing at unsuitable temperatures. It is found by X ray diffraction that there is α Fe in alloy with lower coercivity. In addition, model calculation shows that precipitation of α Fe results in degradation of coercivity. [