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

• US 10,403,314 B2
• Filed: 02/20/2018
• Issued: 09/03/2019
• 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): Renner, Craig A.
• Application Number:
  US15/899,430
• Publication Number:
  US 20180240481A1
• Time in Patent Office: 560 Days
• Field of Search: None
• CPC Class Codes: G11B 5/00813 magnetic tapes
• CPC Class Codes: G11B 5/3909 Arrangements using a magnetic tunnel junction
• CPC Class Codes: G11B 5/584 for track following on tapes
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: G11B 5/78 Tape carriers

Abstract

A magnetic tape device includes a TMR head as a servo head; and a magnetic tape which includes a magnetic layer including ferromagnetic hexagonal ferrite powder and a binding agent, and including a servo pattern. The XRD intensity ratio (Int(110)/Int(114)) of the hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer using an In-Plane method is 0.5 to 4.0. The vertical direction squareness ratio of the magnetic tape is 0.65 to 1.00. The center line average surface roughness Ra measured regarding the surface of the magnetic layer is less than or equal to 2.0 nm, and the logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is less than or equal to 0.050.

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,

the ferromagnetic powder is ferromagnetic hexagonal ferrite powder,

the intensity ratio Int(110)/Int(114) of the peak intensity Int(110) of a diffraction peak of a (110) plane with respect to the peak intensity Int(114) of a diffraction peak of a (114) plane of a hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0,

the vertical direction squareness ratio of the magnetic tape is 0.65 to 1.00,

the center line average surface roughness Ra measured regarding the surface of the magnetic layer 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 0.010 to 0.050, and

the logarithmic decrement on the magnetic layer side is determined by the following method;

securing a measurement sample of the magnetic tape with the measurement surface, which is the surface on the magnetic layer side, facing upward on a substrate in a pendulum viscoelasticity tester;

disposing a columnar cylinder edge which is 4 mm in diameter and equipped with a pendulum 13 g in weight on the measurement surface of the measurement sample such that the long axis direction of the columnar cylinder edge runs parallel to the longitudinal direction of the measurement sample;

raising the surface temperature of the substrate on which the measurement sample has been positioned at a rate of less than or equal to 5°

C./min up to 80°

C.;

inducing initial oscillation of the pendulum;

monitoring the displacement of the pendulum while it is oscillating to obtain a displacement-time curve for a measurement interval of greater than or equal to 10 minutes; and

obtaining the logarithmic decrement Δ

from the following equation;

2. 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.

3. The magnetic tape device according to claim 1,

wherein the vertical direction squareness ratio of the magnetic tape is 0.65 to 0.90.

4. The magnetic tape device according to claim 2,

wherein the vertical direction squareness ratio of the magnetic tape is 0.65 to 0.90.

5. 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.

6. 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 the magnetic layer includes ferromagnetic powder and a binding agent on the non-magnetic support,

the magnetic layer includes the servo pattern,

the ferromagnetic powder is ferromagnetic hexagonal ferrite powder,

the intensity ratio Int(110)/Int(114) of the peak intensity Int(110) of a diffraction peak of a (110) plane with respect to the peak intensity Int(114) of a diffraction peak of a (114) plane of a hexagonal ferrite crystal structure obtained by an X-ray diffraction analysis of the magnetic layer by using an In-Plane method is 0.5 to 4.0,

the vertical direction squareness ratio of the magnetic tape is 0.65 to 1.00,

the center line average surface roughness Ra measured regarding the surface of the magnetic layer 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 0.010 to 0.050, and

the logarithmic decrement on the magnetic layer side is determined by the following method;

securing a measurement sample of the magnetic tape with the measurement surface, which is the surface on the magnetic layer side, facing upward on a substrate in a pendulum viscoelasticity tester;

disposing a columnar cylinder edge which is 4 mm in diameter and equipped with a pendulum 13 g in weight on the measurement surface of the measurement sample such that the long axis direction of the columnar cylinder edge runs parallel to the longitudinal direction of the measurement sample;

raising the surface temperature of the substrate on which the measurement sample has been positioned at a rate of less than or equal to 5°

C./min up to 80°

C.;

inducing initial oscillation of the pendulum;

monitoring the displacement of the pendulum while it is oscillating to obtain a displacement-time curve for a measurement interval of greater than or equal to 10 minutes; and

obtaining the logarithmic decrement Δ

from the following equation;

7. The head tracking servo method according to claim 6,

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

8. The head tracking servo method according to claim 6,

wherein the vertical direction squareness ratio of the magnetic tape is 0.65 to 0.90.

9. The head tracking servo method according to claim 7,

wherein the vertical direction squareness ratio of the magnetic tape is 0.65 to 0.90.

10. The head tracking servo method according to claim 6,

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.