Oxide magnetic material and sintered magnet

Abstract

An oxide magnetic material according to the present invention is represented by the formula: (1−x)CaO.(x/2)R 2 O 3 .(n−y/2)Fe 2 O 3 .yMO, where R is at least one element selected from the group consisting of La, Nd and Pr and always includes La, M is at least one element selected from the group consisting of Co, Zn, Ni and Mn and always includes Co, and the mole fractions x, y and n satisfy 0.4≦x≦0.6, 0.2≦y≦0.35, 4≦n≦6, and 1.4≦x/y≦2.5. The oxide magnetic material includes a ferrite having a hexagonal M-type magnetoplumbite structure as a main phase.

1 . A method of producing an oxide magnetic material having a composition represented by the formula:
   (1 −x )CaO.( x/ 2)R 2 O 3 .( n−y/ 2)Fe 2 O 3   .y MO,   where R is at least one element selected from the group consisting of La, Nd and Pr and always includes La,   M is at least one element selected from the group consisting of Co, Zn, Ni and Mn and always includes Co, and   the mole fractions x, y and n satisfy   0.4≦x≦0.6,   0.2≦y≦0.35,   4≦n≦6, and   1.4≦x/y≦2.5,   wherein the oxide magnetic material consisting essentially of a ferrite having a hexagonal M-type magnetoplumbite structure,   the method comprises the steps of:   preparing a mixed powder to realize a composition represented by the formula;   calcining the mixed powders to form the oxide magnetic material having the composition represented by the formula; and   adding at most 0.2 mass % of H 3 BO 3  before and/or after the step of calcining.   
     
     
         2 . The method of  claim 1 , wherein 4.8≦n≦5.8 is satisfied.