# US 2013/0154035 A1 · Method and system for providing a magnetic tunneling junction using thermally assisted switching

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- Number: US 2013/0154035 A1
- Document ID: US20130154035A1
- Status: Published application
- Kind: A1
- Application number: 13/332,282
- Filed: 2011-12-20
- Published: 2013-06-20
- Earliest claimed: 2011-12-20
- Assignees: Samsung Electronics Co., Ltd.
- Inventors: Mohamad Towfik Krounbi; Dmytro Apalkov; Xueti Tang; Vladimir Nikitin
- Web page: https://patentgrep.com/patent/US20130154035A1

## CPC

- G11C 11/161: {details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell}
- G11C 11/1675: {Writing or programming circuits or methods}
- H01F 10/3254: {the spacer being semiconducting or insulating, e.g. for spin tunnel junction [STJ]}
- H01F 10/3286: {Spin-exchange coupled multilayers having at least one layer with perpendicular magnetic anisotropy}
- 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}
- H10N 50/01: Manufacture or treatment
- H10N 50/10: Magnetoresistive devices
- H10N 50/85: Materials of the active region
- G11C: STATIC STORES (semiconductor memory devices H10B)
- H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR

## Abstract

A magnetic junction is described. The magnetic junction includes a pinned layer, a nonmagnetic spacer layer, and a free layer. The magnetic junction may also include an additional nonmagnetic spacer layer and an additional pinned layer opposing the nonmagnetic spacer layer and the pinned layer. The nonmagnetic spacer layer is between the pinned layer and the free layer. The free layer is configured to be switchable using a write current passed through the magnetic junction. The free layer is also configured to be thermally stable in a quiescent state and have a reduced thermal stability due to heating from the write current being passed through the magnetic junction. In some aspects, the free layer includes at least one of a pinning layer(s) interleaved with ferromagnetic layer(s), two sets of interleaved ferromagnetic layers having different Curie temperatures, and a ferrimagnet having a saturation magnetization that increases with temperature between ferromagnetic layers.

## Claims

### Claim 1

A magnetic junction comprising:
a pinned layer;
a nonmagnetic spacer layer;
a free layer, the nonmagnetic spacer layer residing between the pinned layer and the free layer, the free layer being configured to be switchable using a write current passed through the magnetic junction, the free layer being configured to be thermally stable in a quiescent state and have a reduced thermal stability due to heating from the write current being passed through the magnetic junction.

### Claim 2 (depends on 1)

The magnetic junction of claim 1 wherein the free layer includes a plurality of ferromagnetic layers and at least one pinning layer, the at least one pinning layer being interleaved with the plurality of ferromagnetic layers, the plurality of ferromagnetic layers being ferromagnetically aligned, a first ferromagnetic layer of the plurality of ferromagnetic layers adjoining the nonmagnetic spacer layer, a second ferromagnetic layer of the plurality of ferromagnetic layers being at an opposing side of the free layer from the first ferromagnetic layer.

### Claim 3 (depends on 2)

The magnetic junction of claim 2 wherein the at least one pinning layer is at least one antiferromagnet.

### Claim 4 (depends on 3)

The magnetic junction of claim 3 wherein the at least one antiferromagnet includes at least one of IrMn, PtMn, and FeRh.

### Claim 5 (depends on 3)

The magnetic junction of claim 3 wherein the at least one antiferromagnet has a thickness of at least one nanometer and not more than fifty nanometers.

### Claim 6 (depends on 2)

The magnetic junction of claim 2 further comprising:
an additional nonmagnetic spacer layer, the free layer being between the nonmagnetic spacer layer and the additional nonmagnetic spacer layer, the second ferromagnetic layer adjoining the additional nonmagnetic spacer layer; and
an additional pinned layer, the additional nonmagnetic spacer layer being between the free layer and the additional pinned layer.

### Claim 7 (depends on 6)

The magnetic junction of claim 6 wherein the pinned layer and the additional pinned layer are aligned antiparallel.

### Claim 8 (depends on 1)

The magnetic junction of claim 1 further wherein the free layer includes a first plurality of ferromagnetic layers interleaved with a second plurality of ferromagnetic layers, the first plurality of layers having at least a first Curie temperature, the second plurality of layers having at least a second Curie temperature greater than the at least the first Curie temperature.

### Claim 9 (depends on 8)

The magnetic junction of claim 8 wherein the at least the first Curie temperature is at least one hundred fifty degrees centigrade and not more than five hundred degrees centigrade.

### Claim 10 (depends on 9)

The magnetic junction of claim 9 wherein the at least the second Curie temperature is at least six hundred degrees centigrade and not more than one thousand two hundred degrees centigrade.

### Claim 11 (depends on 8)

The magnetic junction of claim 8 wherein the second plurality of layers has at least one in-plane magnetization.

### Claim 12 (depends on 11)

The magnetic junction of claim 11 wherein the first plurality of layers and the second plurality of layers has an aspect ratio of at least two.

### Claim 13 (depends on 8)

The magnetic junction of claim 8 wherein the second plurality of layers has at least one perpendicular-to-plane magnetization.

### Claim 14 (depends on 13)

The magnetic junction of claim 13 wherein the first plurality of layers has at least one additional perpendicular-to-plane magnetization.

### Claim 15 (depends on 8)

The magnetic junction of claim 8 further comprising:
an additional pinned layer; and
an additional spacer layer between the free layer and the additional pinned layer.

### Claim 16 (depends on 15)

The magnetic junction of claim 15 wherein the free layer further includes at least one pinning layer between a first portion of the first plurality of layers and a second portion of the second plurality of layers.

### Claim 17 (depends on 1)

The magnetic junction of claim 1 wherein the free layer includes a first magnetic layer, a second magnetic layer, and a ferrimagnet between the first and second magnetic layers, the ferrimagnet having a saturation magnetization that increases with increasing temperature.

### Claim 18 (depends on 17)

The magnetic junction of claim 17 wherein the ferrimagnet includes a first sublattice and a second sublattice, the first sublattice having a first Curie temperature, the second sublattice having a second Curie temperature greater than the first Curie temperature.

### Claim 19 (depends on 17)

The magnetic junction of claim 17 wherein the first ferromagnetic layer and the second ferromagnetic layer include CoFeB.

### Claim 20 (depends on 17)

The magnetic junction of claim 17 wherein the magnetic junction further includes:
an additional ferrimagnet, the second ferromagnetic layer residing between the additional ferrimagnet and the ferrimagnet; and
a third ferromagnetic layer, the additional ferrimagnet residing between the second ferromagnetic layer and the third ferromagnetic layer.

### Claim 21 (depends on 17)

The magnetic junction of claim 17 further comprising:
an additional pinned layer; and
an additional spacer layer between the free layer and the additional pinned layer.

### Claim 22 (depends on 1)

The magnetic junction of claim 1 further comprising:
a first thermal barrier adjacent to the pinned layer; and
a second thermal barrier on a side of the magnetic junction opposite to the pinned layer.

### Claim 23

A magnetic memory comprising:
a plurality of magnetic memory cells, each of the magnetic memory cells including at least one magnetic junction, the at least one magnetic junction including a first pinned layer, a first tunneling barrier layer, a free layer, a second tunneling barrier layer, and a second pinned layer, the free layer configured to be thermally stable in a quiescent state and have a reduced thermal stability due to heating from the write current being passed through the magnetic junction, the free layer including a plurality of ferromagnetic layers and at least one antiferromagnetic (AFM) layer, the at least one AFM layer being interleaved with the plurality of ferromagnetic layers, the plurality of ferromagnetic layers being ferromagnetically aligned, a first ferromagnetic layer of the plurality of ferromagnetic layers adjoining the nonmagnetic spacer layer, each of the at least one AFM layer having a thickness of at least one and not more than fifty nanometers, the free layer being configured to be switchable using a write current passed through the magnetic junction, the first tunneling barrier layer being between the first pinned layer and the free layer, a second ferromagnetic layer of the plurality of ferromagnetic layers adjoining the second tunneling barrier layer, the second tunneling barrier layer residing between the second pinned layer and the free layer; and
a plurality of bit lines coupled with the plurality of magnetic memory cells.

### Claim 24

A magnetic memory comprising:
a plurality of magnetic memory cells, each of the magnetic memory cells including at least one magnetic junction, the at least one magnetic junction including a first pinned layer, a first tunneling barrier layer, a free layer, a second tunneling barrier layer, and a second pinned layer, the free layer configured to be thermally stable in a quiescent state and have a reduced thermal stability due to heating from the write current being passed through the magnetic junction, the free layer including a first plurality of ferromagnetic layers interleaved with a second plurality of ferromagnetic layers, the first plurality of layers having at least a first Curie temperature of at least one hundred fifty and not more than five hundred degrees centigrade, the second plurality of layers having at least a second Curie temperature of at least six hundred and not more than one thousand two hundred degrees centigrade, the free layer being configured to be switchable using a write current passed through the magnetic junction, the first tunneling barrier layer being between the first pinned layer and the free layer, the second tunneling barrier layer residing between the second pinned layer and the free layer; and
a plurality of bit lines coupled with the plurality of magnetic memory cells.

### Claim 25

A magnetic memory comprising:
a plurality of magnetic memory cells, each of the magnetic memory cells including at least one magnetic junction, the at least one magnetic junction including a first pinned layer, a first tunneling barrier layer, a free layer, a second tunneling barrier layer, and a second pinned layer, the free layer configured to be thermally stable in a quiescent state and have a reduced thermal stability due to heating from the write current being passed through the magnetic junction, the free layer including a first magnetic layer, a second magnetic layer, and a ferrimagnet between the first and second magnetic layers, the ferrimagnet having a saturation magnetization that increases with increasing temperature, the ferrimagnet including a first sublattice and a second sublattice, the first sublattice having a first Curie temperature, the second sublattice having a second Curie temperature greater than the first Curie temperature, the free layer being configured to be switchable using a write current passed through the magnetic junction, the second tunneling barrier layer residing between the second pinned layer and the free layer; and
a plurality of bit lines coupled with the plurality of magnetic memory cells.

### Claim 26

A method for providing a magnetic junction comprising:
providing a pinned layer;
providing a nonmagnetic spacer layer;
providing a free layer, the nonmagnetic spacer layer residing between the pinned layer and the free layer, the free layer being configured to be switchable using a write current passed through the magnetic junction, the free layer being configured to be thermally stable in a quiescent state and have a reduced thermal stability due to heating from the write current being passed through the magnetic junction.

### Claim 27 (depends on 26)

The method of claim 26 further comprising:
providing an additional nonmagnetic spacer layer, the free layer being between the nonmagnetic spacer layer and the additional nonmagnetic spacer layer, the second ferromagnetic layer adjoining the additional nonmagnetic spacer layer; and
providing an additional pinned layer, the additional nonmagnetic spacer layer being between the free layer and the additional pinned layer.

### Claim 28 (depends on 27)

The method of claim 27 wherein the free layer includes a plurality of ferromagnetic layers and at least one pinning layer, the at least one pinning layer being interleaved with the plurality of ferromagnetic layers, the plurality of ferromagnetic layers being ferromagnetically aligned, a first ferromagnetic layer of the plurality of ferromagnetic layers adjoining the nonmagnetic spacer layer, a second ferromagnetic layer of the plurality of ferromagnetic layers being at an opposing side of the free layer from the first ferromagnetic layer.

### Claim 29 (depends on 28)

The method of claim 28 wherein the at least one pinning layer is at least one antiferromagnet.

### Claim 30 (depends on 27)

The method of claim 27 further wherein the free layer includes a first plurality of ferromagnetic layers interleaved with a second plurality of ferromagnetic layers, the first plurality of layers having at least a first Curie temperature, the second plurality of layers having at least a second Curie temperature greater than the at least the first Curie temperature.

### Claim 31 (depends on 30)

The method of claim 30 wherein the at least the first Curie temperature is at least one hundred fifty degrees centigrade and not more than five hundred degrees centigrade and wherein the at least the second Curie temperature is at least six hundred degrees centigrade and not more than one thousand two hundred degrees centigrade.

### Claim 32 (depends on 31)

The method of claim 31 wherein the second plurality of layers has at least one perpendicular-to-plane magnetization.

### Claim 33 (depends on 32)

The method of claim 32 wherein the first plurality of layers has at least one additional perpendicular-to-plane magnetization.

### Claim 34 (depends on 27)

The method of claim 27 wherein the free layer includes a first magnetic layer, a second magnetic layer, and a ferrimagnet between the first and second magnetic layers, the ferrimagnet having a saturation magnetization that increases with increasing temperature.

### Claim 35 (depends on 34)

The method of claim 34 wherein the ferrimagnet includes a first sublattice and a second sublattice, the first sublattice having a first Curie temperature, the second sublattice having a second Curie temperature greater than the first Curie temperature.

### Claim 36 (depends on 34)

The method of claim 34 wherein the first ferromagnetic layer and the second ferromagnetic layer include CoFeB.