A sintered ferrite magnet comprising main phases of ferrite having a hexagonal M-type magnetoplumbite structure, first grain boundary phases existing between two main phases, and second grain boundary phases existing among three or more main phases, the second grain boundary phases being dispersed in its arbitrary cross section, and the second grain boundary phases having an average area of less than 0.2 m.sup.2, are produced by calcining, pulverizing, molding and sintering raw material powders having the general formula of Ca.sub.1-x-yLa.sub.xA.sub.yFe.sub.2n-zCo.sub.z, wherein 1xy, x, y and z and n representing a molar ratio are in desired ranges; 1.8% or less by mass of SiO.sub.2 and 2% or less by mass (as CaO) of CaCO.sub.3 being added to a calcined body after calcining and before molding; and the sintering step being conducted with a temperature-elevating speed of 1-4 C./minute in a range from 1100 C. to a sintering temperature, and a temperature-lowering speed of 6 C./minute or more in a range from the sintering temperature to 1100 C.

A method comprising the steps of mixing raw material powders to a composition comprising metal elements of Ca, La, Sr, Ba, Fe and Co, whose atomic ratios are represented by the general formula of Ca.sub.1-x-yLa.sub.x(Sr.sub.yBa.sub.1-y).sub.yFe.sub.2n-zCo.sub.z, wherein 1xy, x and y are values in a region defined by a coordinate a: (0.470, 0.297, 0.233), a coordinate b: (0.300, 0.392, 0.308), a coordinate c: (0.300, 0.300, 0.400), a coordinate d: (0.400, 0.200, 0.400) and a coordinate e: (0.470, 0.200, 0.330) in a ternary diagram of x, y, and 1xy, y and z, and n representing a molar ratio meet 0.5y1, 0.2z<0.25, and 5.2<n<5.6; calcining the raw material powder mixture; pulverizing the calcined body; molding the calcined powder; and sintering the resultant green body; 0.1% or more and less than 1.5% by mass of SiO.sub.2 being added to the raw material powder mixture, the calcined body or the calcined powder; and 0-2% by mass (as CaO) of CaCO.sub.3 being added to the calcined body or the calcined powder.

A sintered ferrite magnet comprising metal elements of Ca, La, Fe and Co, whose atomic ratios are represented by the general formula of Ca.sub.1-xLa.sub.xFe.sub.2n-yCo.sub.y, wherein x and y, and n representing a molar ratio meet 0.3x0.6, 0.25y0.5, and 3n6, and further comprising 0.2% to 0.35% by mass of SiO.sub.2.