Oxide magnetic material and sintered magnet
View Patent ↗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 sintered magnet comprising 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 .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,
wherein the oxide magnetic material consists essentially of a ferrite having a hexagonal M-type magnetoplumbite structure, and
wherein the sintered magnet has a coercivity HcJ of 370 kA/m or more.
2. The sintered magnet of claim 1 , wherein 4.8≦n≦5.8 is satisfied.
3. The sintered magnet of claim 1 , wherein M is Co.
4. A sintered magnet comprising 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 .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,
wherein the oxide magnetic material consists essentially of a ferrite having a hexagonal M-type magnetoplumbite structure, and
wherein the sintered magnet has a remanence Br of 0.45 T or more.
5. The sintered magnet of claim 4 , wherein 4.8≦n≦5.8 is satisfied.
6. The sintered magnet of claim 4 , wherein M is Co.
7. A sintered magnet comprising 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 .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,
wherein the oxide magnetic material consists essentially of a ferrite having a hexagonal M-type magnetoplumbite structure, and
wherein the sintered magnet has a loop squareness Hk/HcJ of at least 85%.
8. The sintered magnet of claim 7 , wherein 4.8≦n≦5.8 is satisfied.
9. The sintered magnet of claim 7 , wherein M is Co.
10. The sintered magnet of claim 7 , wherein the loop squareness Hk/HcJ is 90% or more.