Magnetic memory devices based on 4D and 5D transition metal perovskites
Magnetic switching devices, including magnetic memory devices, are provided. The devices use high-quality crystalline films of 4d or 5d transition metal perovskite having a strong spin-orbit coupling (SOC) to produce spin-orbit torque in adjacent ferromagnetic materials via a strong spin-Hall effect. Spin-orbit torque can be generated by the devices with a high efficiency, even at or near room temperature.
1. A magnetic switching device comprising:
a substrate;
a layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite on the substrate, wherein the substrate induces a compressive or tensile strain in the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite;
a layer of ferromagnetic material on the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite;
a first electrode in electrical communication with the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite; and
a second electrode in electrical communication with the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite, wherein the first electrode and the second electrode are configured to pass a charge current through the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite.
2. The device of claim 1 , wherein the 4d or 5d transition metal perovskite is a 5d transition metal perovskite.
3. The device of claim 2 , wherein the 5d transition metal perovskite is a 5d iridate perovskite.
4. The device of claim 3 , wherein the 5d transition metal perovskite has the crystal structure SrIrO 3 .
5. The device of claim 4 , wherein the SrIrO 3 has an in-plane crystallographic orientation of [010].
6. The device of claim 1 , wherein the 4d or 5d transition metal perovskite is a 4d transition metal perovskite.
7. The device of claim 6 , wherein the 4d transition metal perovskite has the crystal structure SrRuO 3 .
8. The device of claim 1 , further comprising a metal oxide capping layer over the layer of ferromagnetic material.
9. The device of claim 1 , wherein the layer of ferromagnetic material comprises a polycrystalline metal alloy.
10. The device of claim 1 , wherein the device is a spin-torque magnetic memory device in which the ferromagnetic layer provides a first ferromagnetic layer of a magnetic tunnel junction and the magnetic tunnel junction further comprises a dielectric spacer layer over the first ferromagnetic layer and a second ferromagnetic layer over the dielectric spacer layer.
11. The device of claim 1 , further comprising a resistance measuring device configured to measure the resistance of the magnetic tunnel junction.
12. A method of switching the magnetic moment of a layer of ferromagnetic material in a magnetic switching device, the magnetic switching device comprising:
a substrate;
a layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite on the substrate, wherein the substrate induces a compressive or tensile strain on the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite;
a layer of ferromagnetic material on the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite;
the method comprising passing a charge current through the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite, whereby a perpendicular spin polarized current is generated in layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite and directed into the layer of ferromagnetic material, producing a spin-orbit torque in the ferromagnetic material that switches the magnetic moment of the ferromagnetic material.
13. A method of reading and writing memory in a spin-torque magnetoresistance random access memory cell, the spin-torque magnetoresistance random access memory cell comprising:
a substrate;
a layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite on the substrate, wherein the substrate induces a compressive strain on the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite; and
a magnetic tunnel junction on the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite, the magnetic tunnel junction comprising:
a free layer interfaced with the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite, the free layer comprising an epitaxial layer of ferromagnetic material;
a dielectric spacer layer on the free layer; and
a fixed layer comprising a ferromagnetic material on the dielectric spacer layer,
the method comprising:
passing an in-plane charge current through the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite, whereby a perpendicular spin polarized current is generated in the layer of electrically conductive, epitaxial, single-crystalline 4d or 5d transition metal perovskite and directed into the free layer, producing a spin-orbit torque in the free layer that switches the magnetic moment of the free layer; and
measuring the resistance of the magnetic tunnel junction.