α" Fe16N2:: A giant magnetic moment material?

Claims that alpha " films have a "giant" magnetic moment have not been substantiated by world-wide activity in which a variety of deposition techniques show very variable results. Moreover, a "giant" moment is incompatible with theory. The controversy makes it desirable to measure the magnetic properties of pure, bulk alpha "-Fe16N2 but, although this has been attempted in several laboratories, the observations are again varied and inconclusive. The present paper shows the occurrence of alpha'-Fe8N with the same chemical composition as alpha "-Fe16N2 but without the latter's N-atom ordering, and so suggests that magnetic variability is due to different degrees of structural order-disorder. Previous Newcastle research showing that alpha " is stabilized by alloying elements which lower the activity coefficient of nitrogen in iron is supported by a recent claim that Ti doping increases the stability of sputtered films. Previous research also shows the existence of alpha "-carbonitrides. Thus, there is scope for a wide exploration of magnetic alpha "-Fe16N2 alloy phases which might be more easily prepared and have greater thermal stability than the binary Fe-N alpha "-phase.