Ferrimagnetic particle powder and manufacturing method therefor, and magnetic recording medium and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-2016372145-A1
Application number	US-201414901884-A
Country	US
Kind code	A1
Filing date	Jul 17, 2014
Priority date	Aug 23, 2013
Publication date	Dec 22, 2016
Grant date	—

Abstract

A magnetic recording medium includes: a substrate; and a magnetic layer including a ferrimagnetic particle powder. A product (V×SFD) of a particle volume V and a holding force distribution SFD of the ferrimagnetic particle is equal to or less than 2500 nm 3 .

First claim

1 . A magnetic recording medium comprising:
a substrate; and a magnetic layer including a ferrimagnetic particle powder, wherein a product (V×SFD) of a particle volume V and a holding force distribution SFD of the ferrimagnetic particle is equal to or less than 2500 nm 3 .

2 . The magnetic recording medium according to claim 1 , wherein the ferrimagnetic particle is a hexagonal ferrite particle.

3 . The magnetic recording medium according to claim 1 , wherein the ferrimagnetic particle has an axial ratio of equal to or less than 3.9.

4 . The magnetic recording medium according to claim 1 , wherein the ferrimagnetic particle has a particle volume of equal to or less than 6000 nm 3 .

5 . The magnetic recording medium according to claim 1 , wherein the ferrimagnetic particle has a holding force distribution of equal to or less than 0.5.

6 . The magnetic recording medium according to claim 1 , wherein a ratio (Vact/V) of an activation volume Vact to a particle volume V for the ferrimagnetic particle is equal to or less than 1.5.

7 . The magnetic recording medium according to claim 2 , wherein the hexagonal ferrite particle contains Ba.

8 . The magnetic recording medium according to claim 7 , wherein the hexagonal ferrite particle further contains at least one selected from the group consisting of Co, Zn, and Ti.

9 . A ferrimagnetic particle powder, wherein a product (V×SFD) of a particle volume V and a holding force distribution SFD is equal to or less than 2500 nm 3 .

10 . A method of manufacturing a ferrimagnetic particle powder, comprising:
melting a ferrimagnetic particle-forming substance and sodium borate to prepare a melt; rapidly cooling the melt to form an amorphous body; and performing a heat treatment to the amorphous body to obtain a ferrimagnetic particle, wherein a temperature T [° C.] and a time t [h] of the heat treatment fall within a range defined by formulas (1) to (5) below:
T= 550 [° C.]  (1)

t=−aT+ 256/3 [h]  (2)

(where, in formula (2), a=2/15 [h/° C.], and 550 [° C.]<T<580 [° C.])
t= 8 [h] (where 580 [° C.]≦ T≦ 650 [° C.])  (3)

t=aT− 236/3 [h]  (4)

(where, in formula (4), a=2/15 [h/° C.], and 650 [° C.]<T<680 [° C.])
T= 680 [° C.]  (5).

11 . The method of manufacturing a ferrimagnetic particle powder according to claim 10 , wherein the temperature T [° C.] and the time t [h] of the heat treatment fall within a range defined by, in addition to the formulas (1) to (5), formula (6) below:
t= 48 [h] (where 550 [° C.]≦ T≦ 680 [° C.])  (6)

12 . The method of manufacturing a ferrimagnetic particle powder according to claim 10 , wherein a ratio of sodium borate to a total of the ferrimagnetic particle-forming substance and sodium borate is more than 30 mol % and less than 50 mol %.

13 . The method of manufacturing a ferrimagnetic particle powder according to claim 10 , wherein the ferrimagnetic particle-forming substance contains barium carbonate and iron oxide.

14 . The method of manufacturing a ferrimagnetic particle powder according to claim 13 , wherein the ferrimagnetic particle-forming substance further contains at least one selected from the group consisting of cobalt oxide, zinc oxide, and titanium oxide.

15 . A method of manufacturing a magnetic recording medium, comprising:
melting a ferrimagnetic particle-forming substance and sodium borate to prepare a melt; rapidly cooling the melt to form an amorphous body; performing a heat treatment to the amorphous body to obtain a ferrimagnetic particle powder; and forming, on a substrate, a magnetic layer containing the ferrimagnetic particle powder, wherein a temperature T [° C.] and a time t [h] of the heat treatment fall within a range defined by formulas (1) to (5) below:
T= 550 [° C.]  (1)

t=−aT+ 256/3 [h]  (2)

(where, in formula (2), a=2/15 [h/° C.], and 550 [° C.]<T<580 [° C.])
t= 8 [h] (where 580 [° C.]≦ T≦ 650 [° C.])  (3)

t=aT− 236/3 [h]  (4)

(where, in formula (4), a=2/15 [h/° C.], and 650 [° C.]<T<680 [° C.])
T= 680 [° C.]  (5).

Assignees

• Sony Corp

Inventors

• Maeshima Katsunori

Classifications

• G11B5/70678 Primary

  Ferrites · CPC title

• G11B5/714

  characterised by the dimension of the magnetic particles · CPC title

• C01G49/0036

  containing one alkaline earth metal, magnesium or lead · CPC title

• C01G49/0009

  Preparation involving a liquid-liquid extraction, an adsorption or an ion-exchange · CPC title

• G11B5/84

  Processes or apparatus specially adapted for manufacturing record carriers · CPC title