# US 2019/0172998 A1 · Magneto-ionic device with a solid state proton pump and methods for using the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0172998 A1 - Document ID: US20190172998A1 - Status: Published application - Kind: A1 - Application number: 16/188,169 - Filed: 2018-11-12 - Published: 2019-06-06 - Earliest claimed: 2017-11-13 - Assignees: Massachusetts Institute of Technology - Inventors: Aik Jun Tan; Geoffrey S. D. Beach - Web page: https://patentgrep.com/patent/US20190172998A1 ## CPC - H10N 50/80: Constructional details - C25B 1/04: by electrolysis of water - C25B 9/19: with diaphragms - 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 10/329: {Spin-exchange coupled multilayers wherein the magnetisation of the free layer is switched by a spin-polarised current, e.g. spin torque effect} - H01F 41/303: {with exchange coupling adjustment of magnetic film pairs, e.g. interface modifications by reduction, oxidation} - H10B 61/00: Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices - H10N 50/10: Magnetoresistive devices - H10N 50/85: Materials of the active region - H10N 59/00: Integrated devices, or assemblies of multiple devices, comprising at least one galvanomagnetic or Hall-effect element covered by groups H10N50/00 - H10N52/00 (MRAM devices H10B61/00) - Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis - H10N: ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR - C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B) - H01F: MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES - H10B: ELECTRONIC MEMORY DEVICES - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A spintronic device controls both the electrical charge and the spin of electrons to transmit, process, and store information. The control of electron spin provides additional degrees of freedom to modify the electric and magnetic properties of materials such as magnetic anisotropy. However, the development and integration of spintronic devices has been limited, in part, by the lack of a robust approach to electrically gate magnetism. Conventional approaches to gating magnetism either exhibit impractically small changes to the properties of a magnet or limited operating lifetime due to material degradation. Here, a magneto-ionic device operates using a hydrogen-gated magneto-ionic mechanism to overcome these shortcomings. A gate voltage applied to the magneto-ionic device causes protons to move towards a magnetic layer where the protons reduce to hydrogen. The presence of hydrogen and protons leads to large changes in the magnetic layer without degradation. This voltage-induced process is reversible. ## Claims ### Claim 1 A magneto-ionic device, comprising: a first electrode; a second electrode; a magnetic layer disposed between the first electrode and the second electrode; and a proton conductor disposed between the magnetic layer and the second electrode, wherein a first gate voltage applied to the first electrode and the second electrode transports protons from the second electrode through the proton conductor toward the magnetic layer where a first portion of the protons are reduced to hydrogen, the hydrogen and a second portion of the protons causing the magnetic layer to switch from a first magnetic state to a second magnetic state. ### Claim 2 (depends on 1) The magneto-ionic device of claim 1, wherein the first magnetic state has a magnetic anisotropy greater than zero and the second magnetic state has a magnetic anisotropy less than zero. ### Claim 3 (depends on 1) The magneto-ionic device of claim 1, wherein the first magnetic state has a magnetic anisotropy greater than 106 erg/cc and the second magnetic state has magnetic anisotropy of at least 10% less the first magnetic anisotropy. ### Claim 4 (depends on 3) The magneto-ionic device of claim 3, wherein the first magnetic state and the second magnetic state each correspond to an out-of-plane magnetization relative to a plane of the magnetic layer, the plane of the magnetic layer being parallel to the first electrode and the second electrode. ### Claim 5 (depends on 1) The magneto-ionic device of claim 1, wherein the proton conductor has a proton conductivity ranging between about 10−10 S/cm and about 10−1 S/cm and an electrical conductivity of less than about 10−10 S/cm. ### Claim 6 (depends on 1) The magneto-ionic device of claim 1, wherein the proton conductor is formed from at least one of gadolinium oxide, terbium oxide, cerium oxide, barium cerium oxide, barium zirconium oxide, yttrium stabilized zirconia, or gadolinium-doped ceria. ### Claim 7 (depends on 1) The magneto-ionic device of claim 1, wherein the proton conductor is formed from an oxide, the oxide forming an oxygen bond between the proton conductor and the magnetic layer that causes the magnetic layer to have an out-of-plane magnetization relative to a plane of the magnetic layer, the plane of the magnetic layer being parallel to the first electrode and the second electrode ### Claim 8 (depends on 1) The magneto-ionic device of claim 1, further comprising: a hydrogen source to provide water molecules, wherein the second electrode catalyzes a water-splitting reaction that splits the water molecules into the protons and oxygen at the interface between the second electrode and the proton conductor. ### Claim 9 (depends on 8) The magneto-ionic device of claim 8, wherein the hydrogen source comprises a hydrogen storage layer disposed between the proton conductor and the second electrode. ### Claim 10 (depends on 1) The magneto-ionic device of claim 1, further comprising: a hydrogen insertion layer, disposed between the magnetic layer and the proton conductor, to store the hydrogen when the first gate voltage is applied to the first electrode and the second electrode and to release the hydrogen when a second gate voltage is applied to the first electrode and the second electrode. ### Claim 11 (depends on 10) The magneto-ionic device of claim 10, wherein the magnetic layer transitions from the first magnetic state to the second magnetic state when hydrogen is stored in the hydrogen insertion layer and the magnetic layer transitions from the second magnetic state to the first magnetic state when hydrogen is released from the hydrogen insertion layer. ### Claim 12 (depends on 11) The magneto-ionic device of claim 11, wherein the first gate voltage is at least about +1.3 V and the second gate voltage less than about 0 V. ### Claim 13 (depends on 10) The magneto-ionic device of claim 10, wherein the hydrogen insertion layer has a thickness of about 3 nm to about 100 nm. ### Claim 14 (depends on 10) The magneto-ionic device of claim 10, wherein the magnetic layer switches between the first magnetic state and the second magnetic state in less than about 1 second. ### Claim 15 (depends on 10) The magneto-ionic device of claim 10, wherein the hydrogen insertion layer has a first current-induced spin-orbit torque when hydrogen is stored in the hydrogen insertion layer and a second current-induced spin-orbit torque when hydrogen is released from the hydrogen insertion layer. ### Claim 16 (depends on 1) The magneto-ionic device of claim 1, further comprising: a third electrode coplanar with and electrically isolated from the second electrode. ### Claim 17 (depends on 1) The magneto-ionic device of claim 1, wherein the magnetic layer is a first magnetic layer, and further comprising: a second magnetic layer disposed between the first electrode and the first magnetic layer; and a tunnel barrier, disposed between the first magnetic layer and the second magnetic layer, to tunnel electrons between the first magnetic layer and the second magnetic layer. ### Claim 18 (depends on 17) The magneto-ionic device of claim 17, the second magnetic layer remains in a third magnetization state while the first magnetic layer switches from the first magnetic state to the second magnetic state. ### Claim 19 (depends on 18) The magneto-ionic device of claim 18, wherein the first magnetic layer is configured to transition from the second magnetic state to the third magnetic state in response to injection of a spin-polarized current into the first magnetic layer. ### Claim 20 (depends on 1) The magneto-ionic device of claim 1, wherein the magnetic layer is a first magnetic layer, and further comprising: a second magnetic layer, disposed between the first magnetic layer and the proton conductor, to reduce degradation of the first magnetic layer; and a coupling spacer disposed between the first magnetic layer and the second magnetic layer. ### Claim 21 A method of reversibly switching a magnetic state of a magneto-ionic device comprising a first electrode, a second electrode, a proton conductor between the first electrode and the second electrode, and a magnetic layer between the proton conductor and the second electrode, the method comprising: applying a first gate voltage to the first electrode and the second electrode from a voltage source, the first gate voltage transporting protons through the proton conductor from the second electrode toward the magnetic layer to reduce a first portion of the protons to hydrogen, the hydrogen and a second portion of the protons causing the magnetic layer to switch from a first magnetic state to a second magnetic state. ### Claim 22 (depends on 21) The method of claim 21, further comprising: catalyzing, by the second electrode, a water-splitting reaction that splits water molecules into the protons and oxygen ions at an interface between the second electrode and the proton conductor. ### Claim 23 (depends on 21) The method of claim 21, further comprising: disconnecting the voltage source from the magneto-ionic device such that the magneto-ionic device operates at open circuit and remains in the second magnetic state. ### Claim 24 (depends on 23) The method of claim 23, further comprising: short-circuiting the magneto-ionic device, the short circuit causing the second portion of the protons to move from the magnetic layer toward the second electrode, thereby causing the magnetic layer to switch from the second magnetic state to the first magnetic state. ### Claim 25 (depends on 24) The method of claim 24, wherein the magneto-ionic device further comprises a hydrogen insertion layer disposed between the proton conductor and the magnetic layer and further comprising at least one of: storing the hydrogen in the hydrogen insertion layer when the magnetic layer transitions from the first magnetic state to the second magnetic state; or releasing the hydrogen from the hydrogen insertion layer when the magnetic layer transitions from the second magnetic state to the first magnetic state. ### Claim 26 (depends on 21) The method of claim 21, further comprising: applying a second gate voltage to the first electrode and the second electrode, the second gate voltage having a polarity opposite to a polarity of the first gate voltage and causing the second portion of the protons to move away from the magnetic layer, thereby switching the magnetic layer from the second magnetic state to the first magnetic state. ### Claim 27 (depends on 21) The method of claim 21, wherein the first magnetic state has a magnetic anisotropy greater than zero and corresponding to an out-of-plane magnetization relative to the plane of the magnetic layer, the plane of the magnetic layer being parallel to the first electrode and the second electrode and further comprising: injecting a spin-polarized current into the magnetic layer to cause the magnetic layer to transition from the second magnetic state to a third magnetic state, the third magnetic state having a magnetic anisotropy greater than zero and corresponding to a magnetization oriented opposite to the first magnetic state; and removing the first gate voltage so as to keep the magnetic layer in the third magnetic state. ### Claim 28 A device comprising: a first electrode; a second electrode to catalyze a water-splitting reaction that splits water molecules into protons and oxygen; a magnetic layer disposed between the first electrode and the second electrode; and a proton conductor, disposed between the magnetic layer and the second electrode, to transport the protons from the second electrode toward the magnetic layer, the protons causing the magnetic layer to switch from a first magnetic state to a second magnetic state.