Magnetoresistive element and method of producing a crystal structure

• US 6,504,469 B1
• Filed: 03/22/2000
• Issued: 01/07/2003
• Est. Priority Date: 03/22/1999
• Status: Expired due to Fees

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Chakalov, Radoslov, Claeson, Tord, Wikborg, Erland, Ivanov, Zdravko
• Primary Examiner(s): Enad, Elvin
• Assistant Examiner(s): LEE, KYUNG S
• Application Number:
  US09/532,467
• Time in Patent Office: 1,021 Days
• Field of Search: 338/32.R, 360/113, 360/126, 428/682, 428/684.T, 428/684.R, 428/692, 428/693, 428/701, 324/207.21, 324/249
• US Class Current: 338/32.00R
• CPC Class Codes: H01F 10/1933 Perovskites
• CPC Class Codes: H10N 50/01 Manufacture or treatment
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: Y10T 428/12958 Next to Fe-base component

Abstract

A magnetoresistive element, comprising a crystal structure with a grain boundary formed at a misorientation angle, and a method of producing a crystal structure having colossal magnetoresistance, wherein a grain boundary is formed at a misorientation angle. The crystal structure comprises a substrate layer and a CMR film layer epitaxially grown thereon, the CMR film layer having a plurality of first sections and a plurality of second sections with intermediate grain boundaries, the crystallographic axis of the first sections being different from the crystallographic axis of the second sections. The method comprises forming, on a base crystal material, a template comprising a first set of sections and a second set of sections with intermediate boundaries, the crystallographic axis of the first set being different from the crystallographic axis of the second set, and growing a film epitaxially on the base crystal material to form a plurality of grain boundaries over the boundaries between the first set and the second set.

Claims

1. A magnetoresistive element comprising a crystal structure with a grain boundary formed at a misorientation angle, wherein the crystal structure comprises a substrate layer and a film layer epitaxially grown thereon, said film layer comprising a perovskite ferromagnetic thin film material having CMR properties, the film layer having a plurality of first sections and a plurality of second sections with intermediate boundaries, said second section further including a seed layer deposited on the substrate layer and selected to predetermine the misorientation angle, the crystallographic axis of the first sections being different from the crystallographic axis of the second sections, and the boundaries comprise grain boundaries, wherein a magnetoresistive response of the element depends on the grain boundaries.

2. An element according to claim 1, wherein:

the substrate comprises single crystals.

3. A device for sensing magnetic signals comprising a crystal structure with a grain boundary formed at a misorientation angle, wherein:

the crystal structure comprises a substrate layer and a film layer epitaxially grown thereon, said film layer comprising a perovskite ferromagnetic thin film material having CMR properties, the film layer having a plurality of first sections and a plurality of second sections with intermediate boundaries, the crystallographic axis of the first sections being different from the crystallographic axis of the second sections, said second section further including a seed layer deposited on the substrate layer and selected to predetermine the misorientation angle;

the boundaries comprise grain boundaries, wherein a magnetoresistive response of the device depends on the grain boundaries; and

the crystal structure is operatively connected to an electronic unit for sensing variations in the resistance of the structure in dependence on a magnetic field acting on the substrate.

4. A magnetoresistive element, comprising:

a substrate layer formed from a material having a crystal structure oriented along a first crystallographic axis;

a seed layer covering portions of the substrate, wherein the seed layer is formed from a material having a crystal structure oriented along a second crystallographic axis that differs from the first crystallographic axis by a misorientation angle, θ

, the seed layer selected to predetermine the misorientation angle;

a buffer layer covering the substrate layer and the seed layer;

a film layer covering the buffer layer, said film layer comprising a perovskite ferromagnetic thin film material having CMR properties, wherein a magnetoresistive response of the element depends on the grain boundaries.

5. A magnetoresistive element according to claim 4, wherein:

the buffer layer is formed from a material having a crystal structure that matches the substrate layer and the seed layer, such that the buffer layer includes a plurality of sections having a crystal structure oriented along the first crystallographic axis and a plurality of sections having a crystal structure oriented along the second crystallographic axis.

6. A magnetoresistive element according to claim 5, wherein:

the magnetoresistive layer is formed from a material having a crystal structure that matches the buffer layer, such that the magnetoresistive layer includes a plurality of sections having a crystal structure oriented along the first crystallographic axis and a plurality of sections having a crystal structure oriented along the second crystallographic axis.

7. A magnetoresistive element according to claim 5, wherein:

the magnetoresistive layer is formed from a material having a crystal structure that differs from the crystal structure of the buffer layer by a misorientation angle, θ

, such that the magnetoresistive layer includes a plurality of sections having a crystal structure oriented along the first crystallographic axis and a plurality of sections having a crystal structure oriented along the second crystallographic axis.