| 摘要 |
The present invention relates to a sintered magnet, which has one Curie temperature and comprises the primary phase of a hexagonal ferrite in chemical formula A<SUB>1-x</SUB>M<SUB>x</SUB>Fe<SUB>12 -y</SUB>R<SUB>y</SUB>O<SUB>19</SUB>, wherein A represents at least one element selected from Sr, Ba and Ca, M represents at least one element selected from the group consisting of rare earth elements and Bi, and must contain La as essential component, R represents at least one element selected from Co, Mn, Zn, Ge and As, and must contain Co as essential component, and the chemical valence of Co is +3, the subscript x and y are the molar ratio, 0<=x<=0.5, 0<=y<=0.5, x and y are not zero at the same time. The present invention provides another sintered magnet, which has one Curie temperature and comprises the primary phase of a hexagonal ferrite in chemical formula A<SUB>1</SUB>. <SUB>x</SUB>M<SUB>x</SUB>[(Fe(III)<SUB>a</SUB>Fe(II)<SUB>1-a</SUB>)<SUB>12-y</SUB>R<SUB>y</SUB>]<SUB>z</SUB>O<SUB>19</SUB>, wherein A represents Sr or/and Ba, M represents at least one element selected from the group consisting of rare earth elements and Bi, and must contain La as essential component, R represents at least one element selected from Co, Ti, Mn, Zn, Ge, As and W, and must contain Co as essential component, and the chemical valence of Co is +3, the subscript x, y, z and a are the molar ratio, 0.05<=x<=0.5, 0.05<=y<=0.5, 0.8<=1.2, 0.997<=a<=0.9995. The process for producing above-mentioned sintered magnet includes the first mixing and presintering, which cause the crystal structure of the ferrite almost perfect and the crystal grain compact. Then the mixture is secondly sintered after adding a little of additives. In this way the density of the sintered magnet is increased, besides the growth of the grain is prohibited in the process of sintering, so both Br and HcJ of the ferrite magnet are increased. Further, the crystal magnetic anisotropy constant K<SUB>1 </SUB>and the intrinsic coercive force (HcJ) are improved and optimal magnetic property is obtained, the technique of the prior art is greatly simplified by means of addition of Co<SUP>3+</SUP> and optimization of the ration of the raw materials.
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