High coercive force 2–17type Sm 1− xEr x(Co 0.69Fe 0.22Cu 0.08Zr 0.02) 7.22 magnets with a low temperature coefficient

Abstract

High energy permanent magnet alloys with internal temperature compensation corresponding to the formula Sm 1− x Er x (Co 0.69Fe 0.22Cu 0.08 Zr 0.02 7.22 ( x = 0, 0.2, 0.4) were characterized by optical metallography, combined scanning electron microscopy and energy-dispersive X-ray analysis, electron microprobe analysis and X-ray diffraction. Sintered magnets were prepared from the induction-melted alloys, ground in the as-cast and homogenized states and sintered with and without a sintering aid. Reversible temperature coefficients α and salient magnetic properties were also investigated. A near-zero temperature coefficient was achieved at an erbium content of x = 0.4. The alloy with an erbium content of x = 0.2 produced a higher energy product and coercivity with a greater, but still usefully low, temperature coefficient. These results indicate that erbium-containing alloy compositions, with proper sintering, solutioning, isothermal aging and controlled cooling heat treatments, can achieve a very high coercive force combined with the desired thermal magnetic behavior for many device applications.