| 简介 |
PROBLEM TO BE SOLVED : To provide a sintered magnet which is possessed of an extremely excellent coercive force and excellent temperature characteristics of residual magnetic flux density, by a method wherein an M-type ferrite phase and a spinel ferrite phase are coexistent with each other in the sintered magnet. SOLUTION : Magnet powder and a sintered magnet are of hexagonal ferrite composition of magnetic plumbite type M phase. More concretely, the ferrite contains A and R, wherein A denotes elements selected out of Sr, Ba, Ca and Pb and must contain Sr, Ca or Ba, and R denotes elements selected from rare earth elements (including Y) and Bi. At this point, it is ascertained by an X-ray diffraction method that an M-type ferrite phase and a spinel ferrite phase are coexistent with each other in the sintered magnet. The sintered magnet has two different Curie points. The sintered magnet has physical properties where the absolute value of a temperature coefficient of a coercive force is 0.25%/ deg.C or less at a temperature of -50 to 50 deg.C., and the absolute value of temperature characteristics of saturation magnetization is 0.18%/ deg.C in a temperature range of a room temperature (25 deg.C) to +125 deg.C. |
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