Fe-Pt-Nb系合金の磁石特性

Abstract

The permanent magnet properties and the temperature dependences 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 γ phase region and subsequent tempering at about 850-900 K in the γ1 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 heattreatments 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 γ1 phase of the initial ordering state which induce the pinning of the magnetic domain wall.