Patent ID: 6419723
Filing Date: 2002-07-16
Classification: H01F

Abstract:
A rare earth permanent magnet which is a sintered block of a powder of a thin alloy ribbon prepared by the strip casting method from a melt of an alloy comprising a rare earth element R selected from the group consisting of praseodymium, neodymium, terbium and dysprosium, element T which is iron or a combination of iron with a transition metal element other than iron and rare earth elements and boron B, which comprises from 1 to 10% by volume fraction of a four-phase coexisting region consisting of an &agr;iron phase having an average grain diameter of 0.1 to 20 &mgr;m, R-rich phase having an average grain diameter of 0.1 to 20 &mgr;m, RXT4B4 phase, the subscript x being a number larger than 1 but smaller than 1.2, having an average grain diameter of 0.1 to 10 &mgr;m and R2T14B phase having an average grain diameter of 0.1 to 20 &mgr;m and from 1 to 30% by volume fraction of a chill crystalline phase having an average grain diameter not exceeding 3 &mgr;m, the balance of the volume fractions consisting of a combination of the R-rich phase, RXT4B4 phase and R2T14B phase of a combination of the R-rich phase and R2T4B phase.