US 7,095,581 B2Granted

Magnetic recording and reproducing apparatus with recording layer having predeterminded convex-concase pattern

AssigneeTDK Corporation

InventorKatsumichi Tagami

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Abstract

A convex structure, where a servo signal is recorded, of a perpendicular magnetic recording medium is set to a truncated quadrangular pyramid shape and a specification of the truncated quadrangular pyramid shape and so forth are determined according to properties of the perpendicular magnetic recording medium to be used, so that the influence of a demagnetizing field that accelerates thermal fluctuation of the perpendicular magnetic recording medium can be reduced in a servo area of the medium which is most affected by the thermal fluctuation of the medium. Therefore, it is possible to provide a magnetic recording and reproducing apparatus having the magnetic recording medium that can suppress degradation of the servo signal caused by the thermal fluctuation of magnetization of perpendicular magnetic recording layers forming a convex-concave structure in the servo area to thereby ensure a stable servo function over the long term.

Claims18

Dependent claims

A magnetic recording and reproducing apparatus comprising a magnetic recording medium having a data information recording portion and a servo information portion for tracking, and a magnetic head for detecting servo information of said servo information portion and recording and reproducing data information on and from said data information recording portion, wherein

said servo information portion is composed of perpendicular magnetic recording layers formed by convex portions based on a predetermined convex-concave pattern, said servo information portion comprising a burst portion where burst signals for tracking are recorded,
said burst portion is formed by disposing at predetermined positions the perpendicular magnetic recording layers in the form of the convex portions where the burst signals are recorded,
said perpendicular magnetic recording layer in the form of the convex portion has a first and a second substantially trapezoidal shape in a track width direction (track radial direction) and in a track circumferential direction, respectively, and
when an upper side corresponding to an upper surface of said perpendicular magnetic recording layer in the form of the convex portion is given as W1 and a lower side corresponding to a lower surface of said perpendicular magnetic recording layer in the form of the convex portion is given as W2 in said first trapezoidal shape in the track width direction,
an upper side corresponding to the upper surface of said perpendicular magnetic recording layer in the form of the convex portion is given as L1 and a lower side corresponding to the lower surface of said perpendicular magnetic recording layer in the form of the convex portion is given as L2 in said second trapezoidal shape in the track circumferential direction,
a thickness of said perpendicular magnetic recording layer in the form of the convex portion is given as t (equal to a height from W2 being the lower side of said convex magnetic recording layer to W1 being the upper side thereof, and equal to a height from L2 to L1), and
a coercive force, a saturation magnetization, and a coercive force squareness ratio in a direction perpendicular to the film plane of said perpendicular magnetic recording layer in the form of the convex portion are given as Hc, Ms, and S*, respectively,
a specification of said burst portion is set so that said coercive force squareness ratio S* takes a value of 0.8 or more and a relationship of a first inequality is satisfied, said first inequality given as
Hc
·
S
*
>
4
⁢
Ms
(
arctan
⁢
⁢
L1
⁢
⁢
W1
t
⁢
L1
2
+
W1
2
+
t
2
+
arctan
⁢
⁢
L2
⁢
⁢
W2
t
⁢
L2
2
+
W2
2
+
t
2
)
.

51 more elements

said servo information portion is composed of perpendicular magnetic recording layers formed by convex portions based on a predetermined convex-concave pattern,
said servo information portion is formed by disposing at predetermined positions the perpendicular magnetic recording layers in the form of the convex portions where servo signals are recorded, said perpendicular magnetic recording layers in the form of the convex portions including belt-like convex portions each extending in a track radial direction (track width direction),
said belt-like convex portion has a trapezoidal shape with its upper side given as L1 and its lower side given as L2 in a track circumferential direction and has a length 100 times or more a length of L2 in the track radial direction, and
when a thickness of said perpendicular magnetic recording layer in the form of the belt-like convex portion is given as t (equal to a height from L2 being the lower side of said convex magnetic recording layer to L1 being the upper side thereof), and
a coercive force, a saturation magnetization, and a coercive force squareness ratio in a direction perpendicular to the film plane of said perpendicular magnetic recording layer in the form of the belt-like convex portion are given as Hc, Ms, and S*, respectively,
a specification of said belt-like convex portion is set so that said coercive force squareness ratio S* takes a value of 0.8 or more and a relationship of a third inequality is satisfied, said third inequality given as
Hc
·
S
*
>
4
⁢
Ms
(
arctan
⁢
⁢
L1
t
+
arctan
⁢
⁢
L2
t
)
.

25 more elements

Dependencies are inferred from the claim text.

Facts

Application: 11/109,693Filed 20 Apr 2005
Priority: JP 2004-20424812 Jul 2004
Published: US 2006/0007573 A112 Jan 2006
Granted: 22 Aug 2006
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G11B 5/743
Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum: patterned record carriers, wherein the magnetic recording…
B82Y 10/00
Nanotechnology for information processing, storage or transmission
G11B 5/59633
For track following on disks: servo formatting
G11B
Information storage based on relative movement between record carrier and transducer