FERROMAGNETIC TUNNEL JUNCTION ELEMENT AND METHOD OF DRIVING FERROMAGNETIC TUNNEL JUNCTION ELEMENT

• US 20110163400A1
• Filed: 08/28/2008
• Published: 07/07/2011
• Est. Priority Date: 03/06/2008
• Status: Abandoned Application

• Current Assignee: III Holdings 3, LLC (Intellectual Ventures LLC)
• Original Assignee: Fuji Electric Holdings Company Limited (Fuji Electric Systems Company Limited)
• Inventors: Ono, Takuya
• Application Number:
  US12/673,935
• Publication Number:
  US 20110163400A1
• Time in Patent Office: Days
• US Class Current: 257/421
• CPC Class Codes: B82Y 25/00 Nanomagnetism, e.g. magnetoimpedance, anisotropic magnetoresistance, giant magnetoresistance or tunneling magnetoresistance
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: H01F 10/3254 the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]
• CPC Class Codes: H01F 10/3268 the exchange coupling being asymmetric, e.g. by use of additional pinning, by using antiferromagnetic or ferromagnetic coupling interface, i.e. so-called spin-valve [SV] structure, e.g. NiFe/Cu/NiFe/FeMn
• 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: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 50/80 Constructional details
• CPC Class Codes: H10N 50/85 Magnetic active materials

Abstract

In a tunnel junction element having a ferromagnetic free layer, an insulating layer and a ferromagnetic fixed layer, in order to reduce the current necessary for spin-transfer magnetization reversal operation in the tunnel junction element, the ferromagnetic free layer comprises first and second ferromagnetic layers, a nonmagnetic metal layer is provided between these ferromagnetic layers, the nonmagnetic metal layer is such that magnetic coupling is preserved between the first and second ferromagnetic layers, also such that there is no influence on the crystal growth of the first and second ferromagnetic layers, the first ferromagnetic layer and the second ferromagnetic layer are placed such that the first ferromagnetic layer is in contact with the insulating layer, and the second ferromagnetic layer has a smaller magnetization than the first ferromagnetic layer.

Claims

1. A ferromagnetic tunnel junction element, comprising a ferromagnetic free layer, an insulating layer, and a ferromagnetic fixed layer which together with the ferromagnetic free layer sandwiches the insulating layer, wherein

the ferromagnetic free layer comprises a first ferromagnetic layer in contact with the insulating layer, a nonmagnetic metal layer, and a second ferromagnetic layer which together with the first ferromagnetic later sandwiches the nonmagnetic metal layer and which has a saturation magnetization smaller than the saturation magnetization of the first ferromagnetic layer,

the film thickness of the nonmagnetic metal layer is set to a film thickness at which the magnetic coupling between the first ferromagnetic layer and the second ferromagnetic layer is ferromagnetic coupling, and

the magnetization direction of the first ferromagnetic layer is determined according to the magnetization direction of the second ferromagnetic layer.

2. The ferromagnetic tunnel junction element according to claim 1, wherein the first ferromagnetic layer comprises any one among a single metal selected from the magnetic metal group consisting of iron, cobalt, and nickel, or an alloy comprising one metal selected from the magnetic metal group, or a compound comprising one metal selected from the magnetic metal group and metalloid element, and wherein the insulating layer comprises a single crystal or fine crystals or magnesium oxide.

3. The ferromagnetic tunnel junction element according to claim 1, wherein the insulating layer and the first ferromagnetic layer are epitaxially joined with each other, and the material of the nonmagnetic metal layer is selected from materials which prevent mutual influence of the crystallinity of the first and second ferromagnetic layers.

4. The ferromagnetic tunnel junction element according to claim 1 wherein the second ferromagnetic layer is of Permalloy.

5. Magnetic random access memory, comprising as a storage element the ferromagnetic tunnel junction element according to claim 1.

6. Magnetic random access memory, comprising as a storage element the ferromagnetic tunnel junction element according to claim 4.