Rare-earth regenerator material particles, and group of rare-earth regenerator material particles, refrigerator and measuring apparatus using the same, and method for manufacturing the same

1. Regenerator material particles, comprising a rare-earth metal and having an average particle size of 0.045 to 0.5 mm,

wherein a proportion of particles having a ratio of a long diameter to a short diameter of 2 or less is 90% or more by number,

a proportion of particles having a depressed portion haying a length of 1/10 to ½ of a particle circumferential length on a particle surface is 30% or more by number and wherein the depressed portion has a depth of 1/10 or less of a particle diameter, and the depressed portion has a channel-shape or a hole-shape, and

wherein the number of the depressed portion per one regenerator material particle is 1 or 2.

2. The particles of claim 1 , comprising at least one selected from the group consisting of Nd, Er 3 Ni, and HoCu 2 .

3. The particles of claim 1 , comprising Nd.

4. The particles of claim 1 , comprising Er 3 Ni.

5. The particles of claim 1 , comprising HoCu 2 .

6. The particles of claim 1 , wherein the number of the depressed portion per one regenerator material particle is 2.

7. The particles of claim 1 , wherein the number of the depressed portion per one regenerator material particle is 1.

8. A method for manufacturing regenerator material particles according to claim 1 , the method comprising a rare-earth metal, the method comprising:

(a) heating a metal comprising a rare-earth element, to obtain a molten metal, and preliminarily heating a rotary disk to a temperature of 800° C. or more;

(b) supplying the molten metal to a rotary disk having a rotating velocity of 7000 to 11000 rpm in a chamber under an argon atmosphere, to obtain a molten metal having a granular form, wherein the rotary disk has a diameter of 20 to 100 mm; and

(c) rapidly cooling the molten metal having the granular form, to obtain the regenerator particles wherein the molten metal is cooled at such rate that temperature is lowered from 1000° C. to root temperature in 5 seconds or less.

9. The method of claim 8 , wherein the molten metal is supplied through a jetting hole having a diameter of 0.05 to 2 mm.

10. The method of claim 8 , wherein the rotary disk comprises a ceramic.

11. A method for manufacturing regenerator material particles cornprising a rare-earth metal according to claim 1 , the method comprising:

(a) heating a metal comprising a rare-earth element, to obtain a molten metal, and preliminarily heating a rotary nozzle to a temperature of 800° C. or more;

(b) jetting the molten metal from the rotary nozzle having a rotating velocity of 7000 to 11000 rpm in a chamber under an argon atmosphere, to obtain a molten metal having a granular form; and

(c) rapidly cooling the molten metal having the granular form, to obtain the regenerator particles wherein the molten metal is cooled at such a rate that a temperature is lowered from 1000 ° C. to room temperature in 5 seconds or less.

12. The method of claim 11 , wherein a diameter of a jetting hole in the rotary nozzle is 0.05 to 2 mm.

13. Rare-earth regenerator material particles, having:

a particle size of 0.045 to 0.5 mm;

a ratio of a long diameter to a short diameter of 2 or less; and

a depressed portion having a length of 1/10 to ½ of a circumferential length on a particle surface and having a depth of 1/10 or less of a particle diameter, and the depressed portion has a channel-shape or a hole-shape, and

wherein the number of depressed portion per one regenerator material particle is 1 or 2.

14. The particles of claim 13 , comprising at least one selected from the group consisting of Nd, Er 3 Ni, and HoCu 2 .

15. The particles of claim 13 , wherein the number of the depressed portion per one regenerator material particle is 2.

16. The particles of claim 13 , wherein the number of the depressed portion per one regenerator material particle is 1.