# US 10,373,752 B2 · Magnetic materials and devices comprising rare earth nitrides

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- Number: US 10,373,752 B2
- Document ID: US10373752B2
- Status: Granted
- Kind: B2
- Application number: 15/300,753
- Filed: 2015-03-31
- Published: 2017-01-19
- Granted: 2019-08-06
- Earliest claimed: 2014-04-02
- Applicants: Franck Natali; Benjamin John Ruck; Harry Joseph Trodahl; Eva-maria Johanna Anton; James Francis McNulty; Simon Edward Granville
- Inventors: Franck Natali; Benjamin John Ruck; Harry Joseph Trodahl; Eva-maria Johanna Anton; James Francis McNulty; Simon Edward Granville
- Web page: https://patentgrep.com/patent/US10373752B2

## CPC

- H01F 10/126: {containing rare earth metals (H01F10/133 takes precedence)}
- H01F 41/302: {for applying spin-exchange-coupled multilayers, e.g. nanostructured superlattices (spin-exchange-coupled multilayers H01F10/32)}
- H10N 50/01: Manufacture or treatment
- H10N 50/10: Magnetoresistive devices
- H10N 50/85: Materials of the active region
- H01F 10/3254: {the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]}
- H10P 14/3202: {Materials thereof}
- H10P 14/3248: {consisting of two layers}
- H10P 14/3402: {characterised by the chemical composition}
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Disclosed herein are magnetic materials comprising rare earth nitrides and, more particularly, magnetic materials comprising multilayer-structured materials comprising one relatively soft and one relatively hard magnetic layer. The magnetic materials comprise a first ferromagnetic layer, a second ferromagnetic layer, and a blocking layer between and in contact with each of the first 5 and second ferromagnetic layers. The first and second ferromagnetic layers have different coercive fields. The first ferromagnetic layer comprises a first rare earth nitride material and the second ferromagnetic layer comprises a second rare earth nitride material. Also disclosed are methods for preparing the materials. The materials are useful in the fabrication of devices, such as GMR magnetic field sensors, MRAM devices, TMR magnetic field sensors, and magnetic 10 tunnel junctions.

## Claims

### Claim 1

A magnetic material comprising a first ferromagnetic layer, a second ferromagnetic layer, and a blocking layer between and in contact with each of the first and second ferromagnetic layers, wherein the first and second ferromagnetic layers have different coercive fields, and wherein the first ferromagnetic layer comprises a first rare earth nitride material and the second ferromagnetic layer comprises a second rare earth nitride material, and wherein the first and second rare earth nitride materials are each independently selected from the group consisting of praseodymium nitride (PrN), neodymium nitride (NdN), samarium nitride (SmN), europium nitride (EuN), gadolinium nitride (GdN), terbium nitride (TbN), dysprosium nitride (DyN), holmium nitride (HoN), erbium nitride (ErN), thulium nitride (TmN), and ytterbium nitride (YbN), and alloys of any two or more thereof,
wherein the blocking layer is a material selected from the group consisting of LaN, LuN, HfN, AlN, GaN, and (Al,In,Ga)N alloys.

### Claim 2 (depends on 1)

A magnetic material as claimed in claim 1, wherein one or both of the first and second rare earth nitride materials further comprises one or more additional dopant(s).

### Claim 3 (depends on 1)

A magnetic material as claimed in claim 1, wherein the first ferromagnetic rare earth nitride material comprises GdN and the second ferromagnetic rare earth nitride material comprises SmN, or wherein the first ferromagnetic rare earth nitride material comprises SmN and the second ferromagnetic rare earth nitride material comprises GdN.

### Claim 4 (depends on 1)

A magnetic material as claimed in claim 1, wherein the blocking layer is about 1-200 nm thick.

### Claim 5 (depends on 1)

A magnetic material as claimed in claim 1, wherein the magnetic material further comprises a substrate in contact with the first ferromagnetic layer, and wherein the first ferromagnetic layer is epitaxial with the substrate, the blocking layer is epitaxial with the first ferromagnetic layer, and the second ferromagnetic layer is epitaxial with the blocking layer.

### Claim 6 (depends on 1)

A magnetic material as claimed in claim 1, wherein the magnetic material further comprises a capping layer in contact with the second ferromagnetic layer.

### Claim 7

A method of preparing a magnetic material, the magnetic material comprising a first ferromagnetic layer, a second ferromagnetic layer, and a blocking layer between and in contact with each of the first and second ferromagnetic layers, wherein the first and second ferromagnetic layers have different coercive fields, and wherein the first ferromagnetic layer comprises a first rare earth nitride material and the second ferromagnetic layer comprises a second rare earth nitride material, and wherein the first and second rare earth nitride materials are each independently selected from the group consisting of praseodymium nitride (PrN), neodymium nitride (NdN), samarium nitride (SmN), europium nitride (EuN), gadolinium nitride (GdN), terbium nitride (TbN), dysprosium nitride (DyN), holmium nitride (HoN), erbium nitride (ErN), thulium nitride (TmN), and ytterbium nitride (YbN), and alloys of any two or more thereof, the method comprising the steps of:
(a) depositing the first ferromagnetic layer comprising the first rare earth nitride material;
(b) depositing the blocking layer on the first ferromagnetic layer formed in step (a); and
(c) depositing the second ferromagnetic layer comprising the second rare earth nitride material on the blocking layer formed in step (b),
wherein the blocking layer is a material selected from the group consisting of LaN, LuN, HfN, AlN, GaN, and (Al,In,Ga)N alloys.

### Claim 8 (depends on 7)

A method as claimed in claim 7, wherein one or both of the first and second rare earth nitride materials further comprises one or more additional dopant(s).

### Claim 9 (depends on 7)

A method as claimed in claim 7, wherein the first ferromagnetic rare earth nitride material comprises GdN and the second ferromagnetic rare earth nitride material comprises SmN, or wherein the first ferromagnetic rare earth nitride material comprises SmN and the second ferromagnetic rare earth nitride material comprises GdN.

### Claim 10 (depends on 7)

A method as claimed in claim 7, wherein the blocking layer is about 1-200 nm thick.

### Claim 11 (depends on 7)

A method as claimed in claim 7, wherein the first ferromagnetic layer is deposited on a substrate, and wherein the first ferromagnetic layer is epitaxial with the substrate, the blocking layer is epitaxial with the first ferromagnetic layer, and the second ferromagnetic layer is epitaxial with the blocking layer.

### Claim 12 (depends on 7)

A method as claimed in claim 7, wherein the method further comprises:
(d) depositing a capping layer on the second ferromagnetic layer formed in step (c).

### Claim 13 (depends on 7)

A method as claimed in claim 7, wherein one or more of the rare earth nitride materials is deposited by MBE by combining the rare earth and a nitrogen source, and wherein the nitrogen source is selected from the group consisting of pure molecular nitrogen, ammonia, and a source of active nitrogen, or mixtures of any two or more thereof.

### Claim 14 (depends on 13)

A method as claimed in claim 13, wherein the nitrogen source flux is a factor of at least 100 larger than the rare earth flux.

### Claim 15 (depends on 7)

A method as claimed in claim 7, wherein the layers are deposited at ambient or elevated temperatures.

### Claim 16 (depends on 7)

A magnetic material when prepared by a method as claimed in claim 7.

### Claim 17 (depends on 1)

A magnetic device comprising a magnetic material of claim 1 and, optionally, electrical contacts.

### Claim 18 (depends on 17)

A magnetic device as claimed in claim 17, wherein a substrate and/or a capping layer provide electrical contact.

### Claim 19 (depends on 1)

A magnetic material as claimed in claim 1, wherein the coercive field of the ferromagnetic layer having a lower coercive field is less than about 500 Oe.

### Claim 20 (depends on 1)

A magnetic material as claimed in claim 1, wherein the coercive field of the ferromagnetic layer having a higher coercive field is larger than the coercive field of the layer with the lower coercive field by a factor of at least about 2.