Neomax Co., Ltd.

Hitachi Metals, Ltd.

Sumitomo Special Metals Co., Ltd.

Seiichi Hosokawa

Sachio Toyota

Etsushi Oda

Yoshinori Kobayashi

Hiroshi Iwasaki

Yasunobu Ogata

Isamu Furuchi

Shuji Anamoto

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 &#x3bc;m, are produced by calcining, pulverizing, molding and sintering raw material powders having the general formula of CaLaAFeCo, wherein 1&#x2212;x&#x2212;y, x, y and z and n representing a molar ratio are in desired ranges; 1.8% or less by mass of SiOand 2% or less by mass (as CaO) of CaCObeing added to a calcined body after calcining and before molding; and the sintering step being conducted with a temperature-elevating speed of 1-4&#xb0; C./minute in a range from 1100&#xb0; C. to a sintering temperature, and a temperature-lowering speed of 6&#xb0; C./minute or more in a range from the sintering temperature to 1100&#xb0; C.

Sintered ferrite magnet and its production method

A sintered ferrite magnet comprising a first granular ferrite compound phase containing Ca, La, Fe and Co and having a Curie temperature Tcbetween 415&#xb0; C. and 430&#xb0; C., and a second granular ferrite compound phase containing Sr, La, Fe and Co and having a Curie temperature Tcbetween 437&#xb0; C. and 455&#xb0; C., the volume ratio of the first ferrite compound phase being 50-90%, and the volume ratio of the second ferrite compound phase being 10-50%, with their total volume ratio being 95% or more.

An oxide magnetic material includes a ferrite with a hexagonal structure as its main phase. Metallic elements included in the oxide magnetic material are represented by the formula:CaLaSrFeCo,where atomic ratios x, x' and y and a molar ratio n satisfy 0.4&#x2266;x&#x2266;0.6, 0.01&#x2266;x&#x2032;&#x2266;0.3, 0.2&#x2266;y&#x2266;0.45 and 5.2&#x2266;n&#x2266;5.8, respectively.

Oxide magnetic material

An oxide magnetic material according to the present invention is represented by the formula: (1&#x2212;x)CaO.(x/2)RO.(n&#x2212;y/2)FeO.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&#x2266;x&#x2266;0.6, 0.2&#x2266;y&#x2266;0.35, 4&#x2266;n&#x2266;6, and 1.4&#x2266;x/y&#x2266;2.5. The oxide magnetic material includes a ferrite having a hexagonal M-type magnetoplumbite structure as a main phase.

Oxide magnetic material and sintered magnet

A ferrite magnet obtained by adding a ferrite having a hexagonal W-type magnetoplumbite structure to a ferrite having a hexagonal M-type magnetoplumbite structure, in which a portion of Sr, Ba, Pb or Ca is replaced with at least one element that is selected from the group consisting of the rare-earth elements (including Y) and Bi and that always includes La, during the fine pulverization process thereof. By adding a small amount of the element such as Co, Ni, Mn or Zn to the ferrite already having the hexagonal M-type magnetoplumbite structure during the fine pulverization process thereof, the magnetic properties can be improved.

Permanent magnet and method for preparation thereof

A ferrite magnet obtained by adding at least one element selected from the group consisting of Co, Ni, Mn and Zn to a ferrite having a hexagonal M-type magnetoplumbite structure, in which a portion of Sr, Ba, Pb or Ca is replaced with at least one element that is selected from the group consisting of the rare-earth elements (including Y) and Bi and that always includes La, during the fine pulverization process thereof, and then subjecting the mixture to re-calcining and/or sintering process(es). By adding a small amount of the element such as Co, Ni, Mn or Zn to the ferrite already having the hexagonal M-type magnetoplumbite structure during the fine pulverization process thereof, the magnetic properties can be improved.

A ferrite magnet obtained by adding a ferrite having a spinel-type structure to a ferrite having a hexagonal M-type magnetoplumbite structure, in which a portion of Sr, Ba, Pb or Ca is replaced with at least one element that is selected from the group consisting of the rare-earth elements (including Y) and Bi and that always includes La, during the fine pulverization process thereof. By adding a small amount of the element such as Co, Ni, Mn or Zn to the ferrite already having the hexagonal M-type magnetoplumbite structure during the fine pulverization process thereof, the magnetic properties can be improved.

A ferrite magnet obtained by adding either an oxide of Mn or oxides of Mn and Co to a ferrite having a hexagonal M-type magnetoplumbite structure, in which a portion of Sr, Ba, Pb or Ca is replaced with at least one element that is selected from the group consisting of the rare earth elements (including Y) and Bi and that always includes La, during the fine pulverization process thereof, and then subjecting the mixture to re-calcining and/or sintering process(es). By adding a small amount of the element Mn or elements Mn and Co to the ferrite already having the hexagonal M-type magnetoplumbite structure during the fine pulverization process thereof, the magnetic properties can be improved.

The production is performed by calcining ferrite magnetic powder in which La is substituted for part of Sr and Ti, Zn, and Co are substituted for part of Fe at temperatures of 1100&deg; C. to 1450&deg; C. The magnetization is improved by substituting Zn for part of Fe, and by substituting Ti for part of Fe for the purpose of charge compensation. In addition, the coercive force is improved by substituting Co for part of Fe, and by substituting La for part of Sr for the purpose of charge compensation. Ti is used for the charge compensation, so that it is possible to reduce the cost.

Magnet powder and method for preparations thereof

An La&mdash;Co ferrite magnet powder, in which Sr and Fe are replaced with La and Co, respectively, is made by carrying out a calcination process at a temperature higher than 1300&deg; C. and equal to or lower than 1450&deg; C. Fe has a magnetic moment oriented upwardly with respect to a crystal c-axis at a number of sites thereof, and also has an opposite magnetic moment oriented downwardly with respect to the crystal c-axis at another number of sites thereof. And Fe is replaced with Co at the greater number of sites thereof. As a result, high coercivity is attained. In this manner, coercivity can be increased while suppressing decrease in saturation magnetization &sgr; .

Growing community of inventors

Takarazuka, Japan

Seiichi Hosokawa