# US 10,374,148 B1 · Multi-resistance MRAM

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- Number: US 10,374,148 B1
- Document ID: US10374148B1
- Status: Granted
- Kind: B1
- Application number: 15/959,837
- Filed: 2018-04-23
- Published: 2019-08-08
- Granted: 2019-08-06
- Earliest claimed: 2018-02-08
- Assignees: SanDisk Technologies LLC
- Applicants: SanDisk Technologies LLC
- Inventors: Young-Suk Choi; Won Ho Choi
- Web page: https://patentgrep.com/patent/US10374148B1

## CPC

- H10N 50/80: Constructional details
- G06N 3/0499: Feedforward networks
- G06N 3/063: using electronic means
- G11C 11/005: {comprising combined but independently operative RAM-ROM, RAM-PROM, RAM-EPROM cells}
- 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}
- G11C 11/54: using elements simulating biological cells, e.g. neuron
- H10B 61/00: Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
- H10N 50/10: Magnetoresistive devices
- G11C 11/401: forming cells needing refreshing or charge regeneration, i.e. dynamic cells
- H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- G06N: COMPUTING ARRANGEMENTS BASED ON SPECIFIC COMPUTATIONAL MODELS
- G11C: STATIC STORES (semiconductor memory devices H10B)
- H10B: ELECTRONIC MEMORY DEVICES

## Abstract

Apparatuses, systems, and methods are disclosed for magnetoresistive random access memory. A magnetic tunnel junction (MTJ) for storing data may include a reference layer. A free layer of an MTJ may be separated from a reference layer by a barrier layer. A free layer may be configured such that one or more resistance states for an MTJ correspond to one or more positions of a magnetic domain wall within the free layer. A domain stabilization layer may be coupled to a portion of a free layer, and may be configured to prevent migration of a domain wall into the portion of the free layer.

## Claims

### Claim 1

An apparatus comprising:
a magnetic tunnel junction (MTJ) for storing data, the magnetic tunnel junction comprising:
a reference layer;
a free layer separated from the reference layer by a barrier layer, the free layer configured such that one or more resistance states for the MTJ correspond to one or more positions of a magnetic domain wall within the free layer; and
a domain stabilization layer coupled to a portion of the free layer, the domain stabilization layer configured to prevent migration of the domain wall into the portion of the free layer.

### Claim 2 (depends on 1)

The apparatus of claim 1, wherein the domain stabilization layer comprises an antiferromagnetic layer.

### Claim 3 (depends on 2)

The apparatus of claim 2, wherein the antiferromagnetic layer is configured to induce a unidirectional magnetic anisotropy in the portion of the free layer.

### Claim 4 (depends on 1)

The apparatus of claim 1, wherein the domain stabilization layer comprises a multilayer.

### Claim 5 (depends on 4)

The apparatus of claim 4, wherein the multilayer comprises one or more of: a cobalt/platinum multilayer and a cobalt/palladium multilayer.

### Claim 6 (depends on 4)

The apparatus of claim 4, wherein the multilayer is configured to induce a coercivity increase in the portion of the free layer.

### Claim 7 (depends on 1)

The apparatus of claim 1, wherein the domain stabilization layer is configured to prevent migration of the domain wall into the portion of the free layer by stabilizing a magnetization direction for the portion of the free layer.

### Claim 8 (depends on 1)

The apparatus of claim 1, further comprising a controller configured to increase the resistance state of the MTJ by applying a first write current to move the domain wall in a first direction.

### Claim 9 (depends on 8)

The apparatus of claim 8, wherein the controller is further configured to decrease the resistance state of the MTJ by applying a second write current in a direction opposite to the first write current, to move the domain wall in a second direction opposite to the first direction.

### Claim 10 (depends on 1)

The apparatus of claim 1, wherein the free layer comprises a nucleation region configured to form the domain wall, and an arm extending from the nucleation region, the arm comprising a plurality of pinning sites for pinning the domain wall.

### Claim 11 (depends on 1)

The apparatus of claim 1, further comprising a second domain stabilization layer configured to prevent migration of the domain wall into a second portion of the free layer, wherein the free layer comprises an elongate arm comprising a plurality of pinning sites for pinning the domain wall, the portion of the free layer comprises a first end portion of the arm, and the second portion of the free layer comprises a second end portion of the arm opposite to the first end portion.