US Patent 7090730 R-Fe-B sintered magnet

An R—Fe—B base sintered magnet having a composition of 12–17 at % of R (wherein R stands for at least two of yttrium and rare earth elements and essentially contains Nd and Pr), 0.1–3 at % of Si, 5–5.9 at % of B, 0–10 at % of Co, and the balance of Fe, containing a R2(Fe,(Co),Si)14B intermetallic compound primary phase and at least 1% by volume of an R—Fe(Co)—Si grain boundary phase, and being free of a B-rich phase exhibits a coercive force of at least 10 kOe despite a reduced content of heavy rare earth.