MAGNETIC TAPE DEVICE AND MAGNETIC REPRODUCING METHOD

• US 20180240479A1
• Filed: 02/20/2018
• Published: 08/23/2018
• Est. Priority Date: 02/20/2017
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: KASADA, Norihito, OZAWA, Eiki
• Granted Patent: US 10,497,384 B2
• Time in Patent Office: Days
• CPC Class Codes: G11B 5/00813 magnetic tapes
• CPC Class Codes: G11B 5/00817 on longitudinal tracks only, e.g. for serpentine format recording
• CPC Class Codes: G11B 5/21 the pole pieces being of ferrous sheet metal or other magnetic layers G11B5/1871 takes precedence; in thin film G11B5/31
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/78 Tape carriers

Abstract

The magnetic tape device includes a magnetic tape; and a TMR head as a reproducing head, in which a center line average surface roughness Ra measured regarding a surface of the magnetic layer of the magnetic tape is equal to or smaller than 2.0 nm, a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is equal to or smaller than 0.050, and ΔSFD in a longitudinal direction of the magnetic tape calculated by Expression 1: ΔSFD=SFD_{25° C.}−SFD_{−190° C.} is equal to or smaller than 0.50, wherein, in Expression 1, the SFD_{25° C.} is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of 25° C., and the SFD_{−190° C.} is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of −190° C.

Claims

1. A magnetic tape device comprising:

a magnetic tape; and

a reproducing head,

wherein the reproducing head is a magnetic head including a tunnel magnetoresistance effect type element as a reproducing element,

the magnetic tape includes a non-magnetic support, and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support,

a center line average surface roughness Ra measured regarding a surface of the magnetic layer is equal to or smaller than 2.0 nm,

a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is equal to or smaller than 0.050, and

Δ

SFD in a longitudinal direction of the magnetic tape calculated by Expression 1 is equal to or smaller than 0.50,

Δ

SFD=SFD<sub>25°

C.</sub>−

SFD<sub>−

190°

C.</sub> 

 

Expression 1

in Expression 1, the SFD<sub>25°

C.</sub> is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of 25°

C., and the SFD<sub>−

190°

C.</sub> is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of −

190°

C.

2. The magnetic tape device according to claim 1,

wherein the logarithmic decrement is 0.010 to 0.050.

3. The magnetic tape device according to claim 1,

wherein the center line average surface roughness Ra measured regarding the surface of the magnetic layer is 1.2 nm to 2.0 nm.

4. The magnetic tape device according to claim 2,

wherein the center line average surface roughness Ra measured regarding the surface of the magnetic layer is 1.2 nm to 2.0 nm.

5. The magnetic tape device according to claim 1,

wherein the Δ

SFD is 0.03 to 0.50.

6. The magnetic tape device according to claim 2,

wherein the Δ

SFD is 0.03 to 0.50.

7. The magnetic tape device according to claim 3,

wherein the Δ

SFD is 0.03 to 0.50.

8. The magnetic tape device according to claim 4,

wherein the Δ

SFD is 0.03 to 0.50.

9. The magnetic tape device according to claim 1,

wherein the magnetic tape includes a non-magnetic layer including non-magnetic powder and a binding agent between the non-magnetic support and the magnetic layer.

10. A magnetic reproducing method comprising:

reproducing information recorded on a magnetic tape by a reproducing head,

wherein the reproducing head is a magnetic head including a tunnel magnetoresistance effect type element as a reproducing element,

the magnetic tape includes a non-magnetic support, and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support,

a center line average surface roughness Ra measured regarding a surface of the magnetic layer is equal to or smaller than 2.0 nm,

a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is equal to or smaller than 0.050, and

Δ

SFD in a longitudinal direction of the magnetic tape calculated by Expression 1 is equal to or smaller than 0.50,

Δ

SFD=SFD<sub>25°

C.</sub>−

SFD<sub>−

190°

C.</sub> 

 

Expression 1

in Expression 1, the SFD<sub>25°

C.</sub> is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of 25°

C., and the SFD<sub>−

190°

C.</sub> is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of −

190°

C.

11. The magnetic reproducing method according to claim 10,

wherein the logarithmic decrement is 0.010 to 0.050.

12. The magnetic reproducing method according to claim 10,

wherein the center line average surface roughness Ra measured regarding the surface of the magnetic layer is 1.2 nm to 2.0 nm.

13. The magnetic reproducing method according to claim 11,

wherein the center line average surface roughness Ra measured regarding the surface of the magnetic layer is 1.2 nm to 2.0 nm.

14. The magnetic reproducing method according to claim 10,

wherein the Δ

SFD is 0.03 to 0.50.

15. The magnetic reproducing method according to claim 11,

wherein the Δ

SFD is 0.03 to 0.50.

16. The magnetic reproducing method according to claim 12,

wherein the Δ

SFD is 0.03 to 0.50.

17. The magnetic reproducing method according to claim 13,

wherein the Δ

SFD is 0.03 to 0.50.

18. The magnetic reproducing method according to claim 10,

wherein the magnetic tape includes a non-magnetic layer including non-magnetic powder and a binding agent between the non-magnetic support and the magnetic layer.