# US 2019/0244646 A1 · Magnetic memory and a method of operating magnetic memory > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0244646 A1 - Document ID: US20190244646A1 - Status: Published application - Kind: A1 - Application number: 16/265,451 - Filed: 2019-02-01 - Published: 2019-08-08 - Earliest claimed: 2018-02-02 - Assignees: National University of Singapore - Applicants: National University of Singapore - Inventors: Jongmin Lee; Rajagopalan Ramaswamy; Hyunsoo Yang - Web page: https://patentgrep.com/patent/US20190244646A1 ## CPC - G11C 11/161: {details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell} - G11C 11/1659: {Cell access} - G11C 11/1673: {Reading or sensing circuits or methods} - 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 10/329: {Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect} - H10B 61/00: Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices - H10N 50/10: Magnetoresistive devices - H10N 50/80: Constructional details - G11C: STATIC STORES (semiconductor memory devices H10B) - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - H10B: ELECTRONIC MEMORY DEVICES - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR ## Abstract In example embodiments, a SOT magnetic memory and operation method are provided that utilize SOT driven domain wall motion to achieve subsequent switching without the need for an external assist magnetic field. The magnetic memory includes a magnetic tunnel junction having a reference layer, a tunnel barrier layer and a free layer, where the tunnel barrier layer is positioned between the reference layer and free layer. A spin-orbit torque layer is disposed adjacent to the free layer. A pair of pinning site are positioned at a longitudinal end of the free layer and each has an opposite magnetization direction from the other. The SOT layer is configured to exert SOT and switch a magnetization direction of the free layer via domain wall motion in a direction of current flow when an electric current is passed through a length of the SOT layer. ## Claims ### Claim 1 A magnetic memory comprising: a magnetic tunnel junction (MTJ) that includes a reference layer, a tunnel barrier layer and a free layer, the tunnel barrier layer positioned between the reference layer and free layer; a spin-orbit torque (SOT) layer disposed adjacent to the free layer; and a pair of pinning sites, each pinning site positioned at a longitudinal end of the free layer and having an opposite magnetization direction from each other, wherein the SOT layer is configured to exert SOT and switch a magnetization direction of the free layer via domain wall motion in a direction of current flow when an electric current is passed through a length of the SOT layer. ### Claim 2 (depends on 1) The magnetic memory of claim 1, wherein the free layer includes tapered regions at the longitudinal ends meeting the pinning sites, wherein the tapered regions have at least one of a tapered width or a tapered thickness such that the pair of pinning sites are at least one of wider or thicker than a portion of the free layer. ### Claim 3 (depends on 2) The magnetic memory of claim 2, wherein the tapered regions have a tapered width such that the pair of pinning sites are wider than the portion of the free layer. ### Claim 4 (depends on 3) The magnetic memory of claim 3, wherein the SOT layer is also tapered at its longitudinal ends such that the longitudinal ends of the SOT layers are wider than the portion of the free layer. ### Claim 5 (depends on 2) The magnetic memory of claim 2, wherein the tapered regions have a tapered thickness such that the pair of pinning sites are thicker than the portion of the free layer. ### Claim 6 (depends on 2) The magnetic memory of claim 2, wherein the tapered regions have both a tapered thickness and a tapered width such that the pair of pinning sites are both wider and thicker than the portion of the free layer. ### Claim 7 (depends on 1) The magnetic memory of claim 1, wherein the SOT layer is configured to switch the magnetization direction of the free layer in the absence of an assist magnetic field. ### Claim 8 (depends on 1) The magnetic memory of claim 1, wherein the pinning sites are configured to provide non-homogenous magnetic anisotropy with respect to the free layer. ### Claim 9 (depends on 1) The magnetic memory of claim 1, wherein at least one of the SOT layer or the free layer is configured to provide non-uniform current density throughout a length thereof. ### Claim 10 (depends on 1) The magnetic memory of claim 1, wherein the magnetized state of the free layer is based on the direction of current flow and on magnetization direction of the pinning sites. ### Claim 11 (depends on 1) The magnetic memory of claim 1, further comprising a device protection layer disposed over the reference layer. ### Claim 12 (depends on 1) The magnetic memory of claim 1, further comprising a first terminal electrically connected to the reference layer, a second terminal electrically connected to the pinning site at one longitudinal end of the SOT layer, and a third terminal electrically connected to the pinning site that the other longitudinal end of the SOT layer. ### Claim 13 The magnetic memory of clause 12, wherein passing electric current through the second and third terminals allows the electric current to be passed through the length of the SOT layer. ### Claim 14 (depends on 1) The magnetic memory of claim 1, wherein the reference layer is biased at a reference magnetic state. ### Claim 15 A magnetic memory comprising: a magnetic tunnel junction (MTJ) that includes a reference layer, a tunnel barrier layer and a free layer, the tunnel barrier layer positioned between the reference layer and free layer; a spin-orbit torque (SOT) layer disposed adjacent to the free layer; and a pair of pinning sites, each pinning site positioned at a longitudinal end of the free layer and having an opposite magnetization direction from each other, wherein the free layer includes tapered regions at the longitudinal ends meeting the pinning sites, wherein the tapered regions have at least one of a tapered width or a tapered thickness such that the pair of pinning sites are at least one of wider or thicker than a portion of the free layer. ### Claim 16 (depends on 15) The magnetic memory of claim 15, wherein the SOT layer is configured to switch the magnetization direction of the free layer in the absence of an assist magnetic field. ### Claim 17 (depends on 15) The magnetic memory of claim 15, wherein the pinning sites are configured to provide non-homogenous magnetic anisotropy with respect to the free layer. ### Claim 18 (depends on 15) The magnetic memory of claim 15, wherein at least one of the SOT layer or the free layer is configured to provide non-uniform current density throughout a length thereof. ### Claim 19 A method for operating a magnetic memory that includes a magnetic tunnel junction (MTJ) having a reference layer, a tunnel barrier layer and a free layer, a spin-orbit torque (SOT) layer disposed adjacent to the free layer; and a pair of pinning sites positioned at longitudinal ends of the free layer, comprising writing the magnetic memory by passing a writing current through the SOT layer, which exerts SOT and switches a magnetization direction of the free layer via domain wall motion in a direction of current flow; and reading the magnetic memory by passing a reading current through one of the pinning sites and the reference layer, and determining a stored value based on a measure of the reading current at the reference layer or one of the pinning sites. ### Claim 20 (depends on 19) The method of claim 19, wherein the writing current switches a magnetization direction of the free layer based on both the direction of current flow and on magnetization direction of the pinning sites.