Abstract
The usefulness of a permanent magnet depends on its energy product (BH)max and it is desirable to increase both the coercivity and remanence. Mechanical alloying with its inherent advantage of grain refinement is expected to result in enhanced coercivity. The advantage of grain size refinement by mechanical alloying is fully utilized, if this can lead to remanence enhancement at the same time. Such a thing is possible if nano scale mixture of exchange coupled hard and soft phases are produced. A magnet with such a two phase mixture is called exchange spring magnet. In the present study exchange spring magnets of α-Fe-Nd(Fe, TM)12Nx (where TM=V, Mo) are synthesized by mechanical alloying and a two stage heat treatment. The effect of nitrogenation condition on the magnetic properties has been studied. The optimum nitrogenation temperature was found to be 673 K. Exchange spring magnet of a-Fe-Nd(Fe, Mo)12Nx showed a maximum energy product of 48 kJ/m3 and a spring back of 50%.
