Magnetic tape device and head tracking servo method employing TMR element servo head and magnetic tape with characterized magnetic layer

• US 10,460,756 B2
• Filed: 02/20/2018
• Issued: 10/29/2019
• 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
• Primary Examiner(s): Evans, Jefferson A
• Application Number:
  US15/900,080
• Publication Number:
  US 20180240489A1
• Time in Patent Office: 616 Days
• Field of Search: 360134
• CPC Class Codes: G11B 5/00813 magnetic tapes
• CPC Class Codes: G11B 5/3906 Details related to the use of magnetic thin film layers or to their effects
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11B 5/59633 Servo formatting G11B5/59627, G11B5/59677, G11B5/59683, G11B5/59688 take precedence
• CPC Class Codes: G11B 5/68 comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/706 characterised by the composition of the magnetic material
• CPC Class Codes: G11B 5/74 Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
• CPC Class Codes: G11B 5/78 Tape carriers

Abstract

A magnetic tape device includes: a magnetic tape including a servo pattern on a magnetic layer; and a Tunneling Magnetoresistive (TMR) head as a servo head, in which the 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, the 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 the SFD_{25° C.} is SFD measured in a longitudinal direction of the magnetic tape at a temperature of 25° C., and the SFD_{−190° C.} is 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 servo head,

wherein the servo head is a magnetic head including a tunnel magnetoresistance effect type element as a servo pattern reading 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,

the magnetic layer includes a servo pattern,

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 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.

4. The magnetic tape device according to claim 3,

wherein the Δ

SFD is 0.03 to 0.50.

5. The magnetic tape device according to claim 2,

wherein the Δ

SFD is 0.03 to 0.50.

6. 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.

7. The magnetic tape device according to claim 6,

wherein the Δ

SFD is 0.03 to 0.50.

8. The magnetic tape device according to claim 1,

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 head tracking servo method comprising:

reading a servo pattern of a magnetic layer of a magnetic tape by a servo head in a magnetic tape device,

wherein the servo head is a magnetic head including a tunnel magnetoresistance effect type element as a servo pattern reading 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,

the magnetic layer includes the servo pattern,

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 head tracking servo method according to claim 10,

wherein the logarithmic decrement is 0.010 to 0.050.

12. The head tracking servo 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.

13. The head tracking servo method according to claim 12,

wherein the Δ

SFD is 0.03 to 0.50.

14. The head tracking servo 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.

15. The head tracking servo method according to claim 14,

wherein the Δ

SFD is 0.03 to 0.50.

16. The head tracking servo method according to claim 11,

wherein the Δ

SFD is 0.03 to 0.50.

17. The head tracking servo method according to claim 10,

wherein the Δ

SFD is 0.03 to 0.50.

18. The head tracking servo 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.