# US 2014/0151830 A1 · Method and system for providing magnetic junctions having a graded 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 2014/0151830 A1 - Document ID: US20140151830A1 - Status: Published application - Kind: A1 - Application number: 13/691,873 - Filed: 2012-12-03 - Published: 2014-06-05 - Earliest claimed: 2012-12-03 - Assignees: Samsung Electronics Co., Ltd. - Inventors: Dmytro Apalkov; Vladimir Nikitin; Mohamad Towfik Krounbi - Web page: https://patentgrep.com/patent/US20140151830A1 ## CPC - H10B 61/00: Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] 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} - G11C 11/5607: {using magnetic storage elements} - H10N 50/01: Manufacture or treatment - H10N 50/10: Magnetoresistive devices - H10B: ELECTRONIC MEMORY DEVICES - G11C: STATIC STORES (semiconductor memory devices H10B) - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR ## 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 has a gradient in a critical switching current density (Jc0) such that a first Jc0 of a first portion of the free layer is lower than a second Jc0 of a second portion of the free layer. The second portion of the free layer is further from the nonmagnetic spacer layer than the first portion is. 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 gradient in a critical switching current density (Jc0) such that a first Jc0 of a first portion of the free layer is lower than a second Jc0 of a second portion of the free layer further from the nonmagnetic spacer layer than the first portion; 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 free layer includes a plurality of magnetic layers, a first layer of the plurality of magnetic layers corresponding to the first portion of the free layer, a second layer of the plurality of magnetic layers corresponding to the second portion of the free layer, the second layer being further from the nonmagnetic spacer layer than the first layer. ### Claim 3 (depends on 2) The magnetic junction of claim 2 wherein the plurality of magnetic layers has a thermal stability gradient such that a first thermal stability of the first layer is lower than a second thermal stability of the second layer further from the nonmagnetic spacer layer than the first layer. ### Claim 4 (depends on 2) The magnetic junction of claim 2 wherein the gradient in the critical switching current density corresponds to an anisotropy gradient in a magnetic anisotropy (Hk) such that a first Hk of the first layer is lower than a second Hk of the second layer from the nonmagnetic spacer layer than the first layer. ### Claim 5 (depends on 2) The magnetic junction of claim 2 wherein the gradient in the critical switching current density corresponds to a magnetic gradient in a saturation magnetization (Ms) such that a first Ms of the first layer is lower than a second Ms of the second layer from the nonmagnetic spacer layer than the first layer. ### Claim 6 (depends on 2) The magnetic junction of claim 2 wherein the gradient in the critical switching current density corresponds an anisotropy gradient in a magnetic anisotropy (Hk) and a magnetic gradient in a saturation magnetization (Ms). ### Claim 7 (depends on 6) The magnetic junction of claim 6 wherein the anisotropy gradient is such that at least one of a first Hk of the first layer is lower than a second Hk of the second layer from the nonmagnetic spacer layer than the first layer and a first Ms of the first layer is lower than a second Ms of the second layer from the nonmagnetic spacer layer than the first layer. ### Claim 8 (depends on 2) The magnetic junction of claim 2 wherein the free layer has a perpendicular magnetic anisotropy and an out of plane demagnetization energy, the perpendicular magnetic anisotropy being greater than the out of plane demagnetization energy. ### Claim 9 (depends on 2) The magnetic junction of claim 2 wherein the plurality of magnetic layers have a plurality of thicknesses, the first layer having a first thickness, the second layer having a second thickness, the first thickness being greater than the second thickness. ### Claim 10 (depends on 2) The magnetic junction of claim 2 wherein the plurality of magnetic layers have a plurality of compositions. ### Claim 11 (depends on 2) The magnetic junction of claim 2 wherein the free layer further includes a plurality of nonmagnetic layers interleaved with the plurality of magnetic layers. ### Claim 12 (depends on 11) The magnetic junction of claim 11 wherein the plurality of nonmagnetic sublayers includes at least one of Pd, Pt, Bi, Tb. ### Claim 13 (depends on 11) The magnetic junction of claim 11 wherein the plurality of nonmagnetic layers has a constant thickness and wherein the plurality of magnetic layers has a plurality of thicknesses, the first layer having a first thickness, the second layer having a second thickness, the first thickness being less than the second thickness. ### Claim 14 (depends on 11) The magnetic junction of claim 11 wherein the plurality of nonmagnetic layers has a constant thickness and wherein the plurality of magnetic layers has a plurality of thicknesses, the first layer having a first thickness, the second layer having a second thickness, the first thickness being greater than the second thickness. ### Claim 15 (depends on 11) The magnetic junction of claim 11 wherein the plurality of magnetic layers has a constant thickness and wherein the plurality of nonmagnetic layers has a plurality of thicknesses, a first nonmagnetic layer of the plurality of nonmagnetic layers being closer to the nonmagnetic spacer layer than a second nonmagnetic layer of the plurality of nonmagnetic layers, the first layer having a first thickness, the second layer having a second thickness, the first thickness being less than the second thickness. ### Claim 16 (depends on 11) The magnetic junction of claim 11 wherein the plurality of magnetic layers includes at least one of Co, Fe and Ni. ### Claim 17 (depends on 11) The magnetic junction of claim 11 wherein the free layer further includes: a magnetic insertion layer consisting of at least one of Co, Fe, CoFe, FeB, CoB, and CoFeB. ### Claim 18 (depends on 17) The magnetic junction of claim 17 wherein the magnetic insertion layer adjoins the nonmagnetic spacer layer. ### Claim 19 (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; and an additional pinned layer, the additional nonmagnetic spacer layer being between the free layer and the additional pinned layer; wherein the plurality of magnetic layers in the free layer includes a third layer having a third Jc0 lower than the second Jc0 of the second layer of the plurality of magnetic layers the third layer being closer to the additional nonmagnetic spacer layer than the second layer. ### Claim 20 (depends on 1) The magnetic junction of claim 1 wherein the free layer includes an alloy having at least one ferromagnetic material and at least one additional material, the at least one ferromagnetic material having at least a first gradient in concentration and the at least one additional material having at least a second gradient in concentration such that the free layer has the gradient in Jc0. ### Claim 21 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 including a pinned layer, a nonmagnetic spacer layer, and a free layer, the free layer having a gradient in a critical switching current density (Jc0) such that a first Jc0 of a first portion of the free layer is lower than a second Jc0 of a second portion of the free layer further from the nonmagnetic spacer layer than the first portion, 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. ### Claim 22 (depends on 21) The magnetic memory of claim 21 wherein the free layer includes a plurality of magnetic layers, a first layer of the plurality of magnetic layers corresponding to the first portion of the free layer, a second layer of the plurality of magnetic layers corresponding to the second portion of the free layer, the second layer being further from the nonmagnetic spacer layer than the first layer. ### Claim 23 (depends on 22) The magnetic memory of claim 22 wherein the plurality of magnetic layers has a thermal stability gradient such that a first thermal stability of the first layer is lower than a second thermal stability of the second layer further from the nonmagnetic spacer layer than the first layer. ### Claim 24 (depends on 22) The magnetic memory of claim 22 wherein the gradient in the critical switching current density corresponds to an anisotropy gradient in a magnetic anisotropy (Hk) such that a first Hk of the first layer is lower than a second Hk of the second layer from the nonmagnetic spacer layer than the first layer. ### Claim 25 (depends on 22) The magnetic memory of claim 22 wherein the gradient in the critical switching current density corresponds to a magnetic gradient in a saturation magnetization (Ms) such that a first Ms of the first layer is lower than a second Ms of the second layer from the nonmagnetic spacer layer than the first layer. ### Claim 26 (depends on 22) The magnetic memory of claim 22 wherein the gradient in the critical switching current density corresponds an anisotropy gradient in a magnetic anisotropy (Hk) and a magnetic gradient in a saturation magnetization (Ms). ### Claim 27 (depends on 22) The magnetic memory of claim 22 wherein the free layer has a perpendicular magnetic anisotropy and an out of plane demagnetization energy, the perpendicular magnetic anisotropy being greater than the out of plane demagnetization energy. ### Claim 28 (depends on 22) The magnetic memory of claim 22 wherein the plurality of magnetic layers have a plurality of thicknesses, the first layer having a first thickness, the second layer having a second thickness, the first thickness being greater than the second thickness. ### Claim 29 (depends on 22) The magnetic memory of claim 22 wherein the plurality of magnetic layers have a plurality of compositions. ### Claim 30 (depends on 22) The magnetic memory of claim 22 wherein the free layer further includes a plurality of nonmagnetic layers interleaved with the plurality of magnetic layers. ### Claim 31 (depends on 30) The magnetic memory of claim 30 wherein the plurality of nonmagnetic sublayers includes at least one of Pd, Pt, Tb, Bi. ### Claim 32 (depends on 30) The magnetic memory of claim 30 wherein the plurality of nonmagnetic layers has a constant thickness and wherein the plurality of magnetic layers has a plurality of thicknesses, the first layer having a first thickness, the second layer having a second thickness, the first thickness being less than the second thickness. ### Claim 33 (depends on 32) The magnetic memory of claim 32 wherein the plurality of nonmagnetic layers has a constant thickness and wherein the plurality of magnetic layers has a plurality of thicknesses, the first layer having a first thickness, the second layer having a second thickness, the first thickness being greater than the second thickness. ### Claim 34 (depends on 32) The magnetic memory of claim 32 wherein the plurality of magnetic layers has a constant thickness and wherein the plurality of nonmagnetic layers has a plurality of thicknesses, a first nonmagnetic layer of the plurality of nonmagnetic layers being closer to the nonmagnetic spacer layer than a second nonmagnetic layer of the plurality of nonmagnetic layers, the first layer having a first thickness, the second layer having a second thickness, the first thickness being less than the second thickness. ### Claim 35 (depends on 32) The magnetic memory of claim 32 wherein the free layer further includes: a magnetic insertion layer consisting of at least one of Co, Fe, CoFe, FeB, CoB, and CoFeB. ### Claim 36 (depends on 22) The magnetic memory of claim 22 wherein the at least one magnetic junction further includes: an additional nonmagnetic spacer layer, the free layer being between the nonmagnetic spacer layer and 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; wherein the plurality of magnetic layers in the free layer includes a third layer having a third Jc0 lower than the second Jc0 of the second layer of the plurality of magnetic layers the third layer being closer to the additional nonmagnetic spacer layer than the second layer. ### Claim 37 (depends on 21) The magnetic memory of claim 21 wherein the free layer includes an alloy having at least one ferromagnetic material and at least one additional material, the at least one ferromagnetic material having at least a first gradient in concentration and the at least one additional material having at least a second gradient in concentration such that the free layer has the gradient in Jc0. ### Claim 38 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 gradient in a critical switching current density (Jc0) such that a first Jc0 of a first portion of the free layer is lower than a second Jc0 of a second portion of the free layer further from the nonmagnetic spacer layer than the first portion; 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 39 (depends on 38) The method of claim 38 wherein the free layer includes a plurality of magnetic layers, a first layer of the plurality of magnetic layers corresponding to the first portion of the free layer, a second layer of the plurality of magnetic layers corresponding to the second portion of the free layer, the second layer being further from the nonmagnetic spacer layer than the first layer. ### Claim 40 (depends on 38) The method of claim 38 wherein the free layer includes an alloy having at least one ferromagnetic material and at least one additional material, the at least one ferromagnetic material having at least a first gradient in concentration and the at least one additional material having at least a second gradient in concentration such that the free layer has the gradient in Jc0. ### Claim 41 (depends on 40) The method of claim 40 wherein the step of providing the free layer further includes: co-sputtering the at least one magnetic material and the at least one additional material from a plurality of sputtering targets. ### Claim 42 (depends on 40) The method of claim 40 wherein the step of providing the free layer further includes: depositing the free layer; and annealing the free layer after the step of depositing the free layer. ### Claim 43 (depends on 42) The method of claim 42 wherein the step of annealing the free layer further includes: annealing the free layer in situ. ### Claim 44 (depends on 42) The method of claim 42 wherein the step of annealing the free layer further includes: annealing the free layer ex situ.