Anisotropic rare earth sintered magnet and method for producing the same

2:

• The anisotropic rare earth sintered magnet according to claim 1, wherein a boundary phase containing 20 at % or more R and having a thickness of 20 nm or less is formed between the main phase and the R′(Fe,Co)2 phase.

3:

• The anisotropic rare earth sintered magnet according to claim 1, wherein in the main phase grains, main phase grains not containing Ce in R′ in the center part exist.

4:

• The anisotropic rare earth sintered magnet according to claim 1, wherein in the main phase grains, main phase grains where R′ in the center part is Nd, or Nd and Pr exist.

5:

• The anisotropic rare earth sintered magnet according to claim 1, wherein the R′(Fe,Co)2 phase is a phase showing ferromagneticity or ferrimagneticity at room temperature or higher.

6:

• The anisotropic rare earth sintered magnet according to claim 1, wherein the Ce/R′ ratio in the R′(Fe,Co)2 phase is higher than the Ce/R′ ratio in the outer shell part of the main phase grains.

7:

• The anisotropic rare earth sintered magnet according to claim 1, wherein the Ce/R′ ratio in the R′-rich phase is higher than the Ce/R′ ratio in the outer shell part of the main phase grains.

8:

• The anisotropic rare earth sintered magnet according to claim 1, which contains the R′-rich phase and the R′(Fe,Co)2 phase in a ratio of 1 vol % or more in total.

9:

• The anisotropic rare earth sintered magnet according to claim 1, wherein the Ce/R′ ratio in the composition of the sintered magnet is 0.01 or more and 0.3 or less.

10:

• The anisotropic rare earth sintered magnet according to claim 1, wherein the B-rich phase contained in the sintered magnet is 5 vol % or less.

11:

• The anisotropic rare earth sintered magnet according to claim 1, wherein a two-interparticle grain boundary phase is formed between the adjacent main phase grains.

12:

• The anisotropic rare earth sintered magnet according to claim 11, wherein Ce/R′ in the boundary phase formed between the main phase and the R′(Fe,Co)2 phase is higher than Ce/R′ in the two-interparticle grain boundary phase formed between the adjacent main phase grains.

13:

• The anisotropic rare earth sintered magnet according to claim 1, of which the coercive force at room temperature HcJ(room temperature) is 10 kOe or more, and a value of a temperature coefficient of the coercive force β is β≥(0.01×HcJ(room temperature)−0.720)%/K.

14:

• A method for producing the anisotropic rare earth sintered magnet of claim 1, comprising grinding an alloy that contains an Nd2Fe14B-type crystal compound phase and an alloy having a higher R′ composition ratio and a higher Ce/R′ ratio than the former, followed by mixing and powder-compression molding it in a magnetic field to give a molded product, and then sintering it at a temperature of 800° C. or higher and 1200° C. or lower.

15:

• A method for producing the anisotropic rare earth sintered magnet of claim 1, comprising grinding an alloy that contains an Nd2Fe14B-type crystal compound phase followed by powder-compression molding it in a magnetic field to give a molded product, then sintering it at a temperature of 800° C. or higher and 1200° C. or lower, then bringing the sintered product into contact with a Ce-containing material and heat-treating it at a temperature of 600° C. or higher and a sintering temperature or lower to make Ce diffuse inside the sintered product.

16:

• The method for producing an anisotropic rare earth sintered magnet according to claim 15, wherein the Ce-containing material to be brought into contact with the sintered product is one or more kinds selected from a Ce metal, a Ce-containing alloy and a Ce-containing compound, and the form thereof is one or more kinds selected from a powder, a thin film, a thin strip, a foil and a vapor.

17:

• The method for producing an anisotropic rare earth sintered magnet according to claim 14, wherein the sintered product is heat-treated at a temperature of 300 to 800° C.

18:

• The method for producing an anisotropic rare earth sintered magnet according to claim 14, wherein the sintered product is heat-treated at a temperature of 600 to 1000° C., then cooled down to at least 550° C. or lower at a cooling speed of 1° C./min or more and 50° C./min or less, and then further heat-treated at a temperature of 300 to 800° C.