The Effect of Various Additional Elements on Properties of FePt Permanent Magnets Having High Energy Product

The present authors have previously reported the permanent magnet properties of iron-rich Fe–Pt alloys and a new magnet alloy (Fe-38.5 at%Pt) with a high energy product of 159 kJ·m−3, which was named as Platiron Magnet. In this paper are further studied the effects of additions of Ti, V, Rh, Pd, Ir, Au, Al, Ga and Ge on the magnetic properties of the magnet alloy. The permanent magnet poperties of Fe–Pt alloys can be improved by addition of a small amount of Ti or V. Especially, the alloy containing 60 at% iron, 39 at% platinum and 1 at% titanium shows the highest maximum energy product of 165 kJ·m−3, a coercive force of 360 kA·m−1 and a residual flux density of 1.0 T when aged at 823 K for 1.8 Ms after water-quenching. Further, the alloy containing 60.5 at% iron, 38.5 at% platinum and 1 at% vanadium shows the highest coercive force of 410 kA·m−1, a maximum energy product of 160 kJ·m−3 and a residual flux density of 1.04 T when aged at 773 K for 252 ks after water-quenching. In the case of addition of each of the other elements, however, the permanent magnet properties are remarkably deteriorated.It is presumed that the excellent permanent magnet properties of the Platiron Magnet alloys are related to the existence of the γ1 ordered phase of the Llo-type having high magneto-crystalline anisotropy.