# US 2014/0151831 A1 · Method and system for providing magnetic junctions having a thermally stable and easy to switch magnetic free layer > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0151831 A1 - Document ID: US20140151831A1 - Status: Published application - Kind: A1 - Application number: 14/026,386 - Filed: 2013-09-13 - Published: 2014-06-05 - Earliest claimed: 2012-12-03 - Assignees: Samsung Electronics Co., Ltd. - Applicants: Samsung Electronics Co., Ltd. - Inventors: Eugene Chen; Dmytro Apalkov - Web page: https://patentgrep.com/patent/US20140151831A1 ## CPC - H10N 50/10: Magnetoresistive devices - 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} - H10N 50/01: Manufacture or treatment - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - G11C: STATIC STORES (semiconductor memory devices H10B) ## Abstract A method and system provide a magnetic junction usable in a magnetic device. The magnetic junction includes a pinned layer, a nonmagnetic spacer layer, and a free layer. The nonmagnetic spacer layer is between the pinned layer and the free layer. The free layer includes a plurality of subregions. Each of the subregions has a magnetic thermal stability constant. The subregions are ferromagnetically coupled such that the free layer has a total magnetic thermal stability constant. The magnetic thermal stability constant is such that the each of the subregions is magnetically thermally unstable at an operating temperature. The total magnetic thermal stability constant is such that the free layer is magnetically thermally stable at the operating temperature. The magnetic junction is configured such that the free layer is switchable between a plurality of stable magnetic states when a write current is passed through the magnetic junction. ## Claims ### Claim 1 A magnetic junction for use in a magnetic device comprising: a pinned layer; a nonmagnetic spacer layer; and a free layer having a plurality of subregions, each of the plurality of subregions having a magnetic thermal stability constant, the plurality of subregions being ferromagnetically coupled such that the free layer has a total magnetic thermal stability constant; the magnetic thermal stability constant being such that the each of the plurality of subregions is magnetically thermally unstable at an operating temperature, the total magnetic thermal stability constant being such that the free layer is magnetically thermally stable at the operating temperature; wherein the magnetic junction is configured such that the free layer is switchable between a plurality of stable magnetic states when a write current is passed through the magnetic junction. ### Claim 2 (depends on 1) The magnetic junction of claim 1 wherein the plurality of subregions includes a plurality of magnetic layers interleaved with at least one nonmagnetic. layer. ### Claim 3 (depends on 2) The magnetic junction of claim 2 wherein the plurality of magnetic layers has a first layer an a second layer, the first layer having a first layer magnetization and being closest to the nonmagnetic spacer layer and a second layer having a second layer magnetization and being furthest from the nonmagnetic spacer layer, the first layer magnetization being substantially perpendicular to plane. ### Claim 4 (depends on 3) The magnetic junction of claim 3 wherein the second layer has a second layer magnetization substantially antiparallel to the first layer magnetization, the first layer magnetization having a first magnitude different from a second magnitude of the second layer magnetization. ### Claim 5 (depends on 3) The magnetic junction of claim 3 wherein the free layer has a domain wall therein. ### Claim 6 (depends on 3) The magnetic junction of claim 3 wherein the first layer magnetization is substantially parallel to the second layer magnetization. ### Claim 7 (depends on 2) The magnetic junction of claim 2 wherein the plurality of magnetic layers are substantially identical. ### Claim 8 (depends on 1) The magnetic junction of claim 1 wherein the plurality of subregions correspond to a plurality of grains separated by at least one grain boundary. ### Claim 9 (depends on 1) The magnetic junction of claim 1 wherein the thermal stability constant of each of the plurality of subregions is not more than a quantity, the quantity being eighty multiplied by kb multiplied by the operating temperature. ### Claim 10 (depends on 9) The magnetic junction of claim 9 wherein the quantity is not more than forty multiplied by the kb multiplied by the operating temperature. ### Claim 11 (depends on 1) The magnetic junction of claim 1 wherein the plurality of subregions are configured to switch in an order independent of distance from the nonmagnetic spacer layer. ### Claim 12 A magnetic memory comprising: a plurality of magnetic storage cells, each of the plurality of magnetic storage cells including at least one magnetic junction, the at least one magnetic junction includes a pinned layer, a nonmagnetic spacer layer and a free layer having a plurality of subregions, each of the plurality of subregions having a magnetic thermal stability constant, the plurality of subregions being ferromagnetically coupled such that the free layer has a total magnetic thermal stability constant; the magnetic thermal stability constant being such that the each of the plurality of subregions is magnetically thermally unstable at an operating temperature, the total magnetic thermal stability constant being such that the free layer is magnetically thermally stable at the operating temperature, the magnetic junction being configured such that the free layer is switchable between a plurality of stable magnetic states when a write current is passed through the magnetic junction; and a plurality of bit lines coupled with the plurality of magnetic storage cells. ### Claim 13 (depends on 12) The magnetic memory of claim 12 wherein the plurality of subregions includes a plurality of magnetic layers interleaved with at least one nonmagnetic layer. ### Claim 14 (depends on 13) The magnetic memory of claim 13 wherein the plurality of magnetic layers has a first layer an a second layer, the first layer having a first layer magnetization and being closest to the nonmagnetic spacer layer and a second layer having a second layer magnetization and being furthest from the nonmagnetic spacer layer, the first layer magnetization being substantially perpendicular to plane. ### Claim 15 (depends on 14) The magnetic memory of claim 14 wherein the second layer has a second layer magnetization substantially antiparallel to the first layer magnetization, the first layer magnetization having a first magnitude different from a second magnitude of the second layer magnetization. ### Claim 16 (depends on 14) The magnetic memory of claim 14 wherein the free layer has a domain wall therein. ### Claim 17 (depends on 12) The magnetic memory of claim 12 wherein the plurality of subregions correspond to a plurality of grains separated by at least one grain boundary. ### Claim 18 (depends on 12) The magnetic memory of claim 12 wherein the each of the plurality of subregions has a thermal stability constant of not more than eighty. ### Claim 19 (depends on 1) The magnetic junction of claim 1 wherein the plurality of subregions are configured to switch in an order independent of distance from the nonmagnetic spacer layer. ### Claim 20 A method for providing a magnetic junction for use in a magnetic device comprising: providing a pinned layer; providing a nonmagnetic spacer layer; and providing a free layer having a plurality of subregions, each of the plurality of subregions having a magnetic thermal stability constant, the plurality of subregions being ferromagnetically coupled such that the free layer has a total magnetic thermal stability constant; the magnetic thermal stability constant being such that the each of the plurality of subregions is magnetically thermally unstable at an operating temperature, the total magnetic thermal stability constant being such that the free layer is magnetically thermally stable at the operating temperature; wherein the magnetic junction is configured such that the free layer is switchable between a plurality of stable magnetic states when a write current is passed through the magnetic junction.