PERMANENT-MAGNET PROPERTIES AND THEIR TEMPERATURE-DEPENDENCE IN THE FE-PT-NB ALLOY SYSTEM (REPRINTED FROM J JAPAN INST METALS, VOL 54, PG 1284, 1990)

The permanent magnet properties and the temperature dependence of Fe-Pt-Nb ternary alloys were investigated by using a recording fluxmeter, a vibrating sample magnetometer and an X-ray diffractometer. The excellent permanent magnet properties in the Fe-Pt-Nb system have been obtained by water-quenching from a temperature in the gamma phase region and subsequent tempering at about 850-900 K in the gamma-1 phase region. A typical Fe-39.5 at%Pt-0.75 at%Nb alloy exhibits the highest value of a maximum energy product of 167 kJ.m-3, with a residual flux density of 1.05 T and a coercivity of 398 kA.m-1. These properties are superior to those of the basic binary Fe-Pt alloy. The composition range of the excellent permanent magnet properties of Fe-Pt-Nb ternary alloys spread out wider than that of Fe-Pt magnet alloys, so that the heat-treatments could be controlled easily, and the reproducibility of the magnetic properties would be improved. As a Fe-38Pt-1Nb alloy exhibits the excellent rectangular hysteresis loops at 400 K as well as at 290 K, these magnet alloys have the stable temperature properties and show comparatively high Curie temperature. It is presumed that the excellent permanent magnet properties of the Fe-Pt-Nb alloys originate from the existence of a constitutionally imperfect gamma-1 phase of the initial ordering state which induce the pinning of the magnetic domain wall.