Magnetoresistive effect sensor including a magnet array of a plurality of permanent magnets

• US 7,167,345 B2
• Filed: 06/24/2004
• Issued: 01/23/2007
• Est. Priority Date: 10/23/2002
• Status: Active Grant

• Current Assignee: Yamaha Corporation
• Original Assignee: Yamaha Corporation
• Inventors: Wakui, Yukio, Oohashi, Toshiyuki
• Primary Examiner(s): EVANS, JEFFERSON A
• Application Number:
  US10/874,324
• Publication Number:
  US 20040233588A1
• Time in Patent Office: 943 Days
• Field of Search: 360/313, 360/321
• US Class Current: 360/313
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: B82Y 40/00 Manufacture or treatment of nanostructures
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06
• CPC Class Codes: G01R 33/093 using multilayer structures, e.g. giant magnetoresistance sensors thin magnetic films H01F10/00
• CPC Class Codes: H01F 10/324 Exchange coupling of magnetic film pairs via a very thin non-magnetic spacer, e.g. by exchange with conduction electrons of the spacer
• CPC Class Codes: H01F 10/3295 Spin-exchange coupled multilayers wherein the magnetic pinned or free layers are laminated without anti-parallel coupling within the pinned and free layers
• CPC Class Codes: H01F 13/00 Apparatus or processes for magnetising or demagnetising devices for holding workpieces using magnetic or electric force acting directly on the workpieces B23Q3/15 ; for degaussing ships B63G9/06; for clocks or watches G04D9/00; recording or erasing of information on magnetic record carriers G11B5/00 ; demagnetising arrangements for colour television H04N9/29
• CPC Class Codes: H01F 17/0006 Printed inductances printed coils for dynamo-electric machines H02K3/26; printed circuits H05K
• CPC Class Codes: H01F 41/302 for applying spin-exchange-coupled multilayers, e.g. nanostructured superlattices spin-exchange-coupled multilayers H01F10/32
• CPC Class Codes: Y10T 29/49002 Electrical device making
• CPC Class Codes: Y10T 29/49034 Treating to affect magnetic properties

Abstract

A magnetic sensor provided with a magnetoresistive effect element capable of stably maintaining a direction of magnetization in a magnetic domain of a free layer. The magnetic sensor includes a magnetoresistive effect element provided with narrow zonal portions including a pinned layer and a free layer. Disposed below both ends of the free layer are bias magnet films composed of a permanent magnet that applies to the free layer a bias magnetic field in a predetermined direction and an initializing coil that is disposed in the vicinity of the free layer and applies to the free layer a magnetic field having the direction same as that of the bias magnetic field by being energized under a predetermined condition. Further, magnetizing the bias magnet films and fixing the direction of magnetization of the pinned layer are performed by a magnetic field formed by a magnet array configured such that plural permanent magnets are arranged on a lattice point of a tetragonal lattice and a polarity of a magnet pole of each permanent magnet is different from a polarity of the other adjacent magnet pole spaced by the shortest route.

Claims

1. The magnet array including plural permanent magnets, each having an approximately rectangular parallelepiped shape and having a sectional shape, perpendicular to one central axis of the rectangular parallelepiped, which is approximately square, and each having poles formed at both edge faces, one of which has the approximately square shape perpendicular to the central axis of the rectangular parallelepiped and a thin plate-like yoke formed of a magnetic material;

wherein

the plural permanent magnets are arranged in such a manner that each center of gravity of the edge faces having the approximately square shape is matched with a lattice point of a tetragonal lattice, a certain side of sides forming one of the edge faces of the plural permanent magnets disposed in a certain row of the tetragonal lattice and a certain side of sides forming one of the edge faces of the other plural permanent magnets disposed in the same row of the tetragonal lattice is in a same straight line, all the edge faces having the square shapes of the permanent magnets are placed in an approximately same single plane, and any two of the polarities of the magnetic poles of the permanent magnets disposed adjacent each other and spaced by the shortest route are different each other; and

the yoke comprises plural through holes each of which has a shape which is the approximately same as the sectional shape which is approximately square and the holes being arranged at the positions where the permanent magnets are disposed, and the yoke being arranged in such a manner that the same single plane in which all the edge faces of the permanent magnets are placed is disposed between an upper surface and a lower surface of the yoke when the permanent magnets are inserted into the through holes, wherein the yoke has through openings serving as air gaps formed between the through holes that are adjacent each other and that are spaced by a shortest route.

2. The magnet array claimed in claim 1, wherein the yoke has openings at regions each of which is surrounding a center of gravity of a square drawn by lines connecting the lattice points of the tetragonal lattice in a plan view.

3. The magnet array claimed in claim 1, wherein each of the through holes of the yoke has a square portion having a square shape which is the approximately same as the shape of the sectional square shape of the permanent magnet in a plan view and a margin portions swelling outwardly from the square at each of corners of the square portion.

4. The magnet array including plural permanent magnets, each having an approximately rectangular parallelepiped shape and having a sectional shape, perpendicular to one central axis of the rectangular parallelepiped, which is approximately square, and each having poles formed at both edge faces, one of which has the approximately square shape perpendicular to the central axis of the rectangular parallelepiped and a thin plate-like yoke formed of a magnetic material;

wherein

the plural permanent magnets are arranged in such a manner that each center of gravity of the edge faces having the approximately square shape is matched with a lattice point of a tetragonal lattice, a certain side of sides forming one of the edge faces of the plural permanent magnets disposed in a certain row of the tetragonal lattice and a certain side of sides forming one of the edge faces of the other plural permanent magnets disposed in the same row of the tetragonal lattice is in a same straight line, all the edge faces having the square shapes of the permanent magnets are placed in an approximately same single plane, and any two of the polarities of the magnetic poles of the permanent magnets disposed adjacent each other and snaced by the shortest route are different each other; and

the yoke comprises plural through holes each of which has a shape which is the approximately same as the sectional shape which is approximately square and the holes being arranged at the positions where the permanent magnets are disposed, and the yoke being arranged in such a manner that the same single plane in which all the edge faces of the permanent magnets are placed is disposed between an upper surface and a lower surface of the yoke when the permanent magnets are inserted into the through holes, wherein each of the through holes of the yoke has a square portion having a square shape which is the approximately same as the shape of the sectional square shape of the permanent magnet in a plan view and a margin portions swelling outwardly from the square at each of corners of the square portion.

5. A magnet array including plural permanent magnets, each having an approximately rectangular parallelepiped shape and having a sectional shape, perpendicular to one central axis of the rectangular parallelepiped, which is approximately square, and each having poles formed at both edge faces, one of which has the approximately square shape perpendicular to the central axis of the rectangular parallelepiped and a thin plate-like yoke formed of a magnetic material;

wherein

the plural permanent magnets are arranged in such a manner that each center of gravity of the edge faces having the approximately square shape is matched with a lattice point of a tetragonal lattice, a certain side of sides forming one of the edge faces of the plural permanent magnets disposed in a certain row of the tetragonal lattice and a certain side of sides forming one of the edge faces of the other plural permanent magnets disposed in the same row of the tetragonal lattice is in a same straight line, all the edge faces having the square shapes of the permanent magnets are placed in an approximately same single plane, and any two of the polarities of the magnetic poles of the permanent magnets disposed adjacent each other and spaced by the shortest route are different each other; and

the yoke comprises plural through holes each of which has a shape which is the approximately same as the sectional shape which is approximately square and the holes being arranged at the positions where the permanent magnets are disposed, and the yoke being arranged in such a manner that the same single plane in which all the edge faces of the permanent magnets are placed is disposed between an upper surface and a lower surface of the yoke when the permanent magnets are inserted into the through holes;

wherein

the yoke has through openings serving as air gaps formed between the through holes that are adjacent each other and that are spaced by a shortest route;

wherein

the yoke has openings at regions each of which is surrounding a center of gravity of a square drawn by lines connecting the lattice points of the tetragonal lattice in a plan view;

wherein

each of the through holes of the yoke has a square portion having a square shape which is the approximately same as the shape of the sectional square shape of the permanent magnet in a plan view and a margin portions swelling outwardly from the square at each of corners of the square portion.