Multi-level multiferroic memory device and related methods
An electronic device may include a first electrode, a first magnetostrictive layer coupled to the first electrode, a plurality of alternating ferromagnetic and insulating layers stacked above the first magnetostrictive layer, a second electrode electrically coupled to an intermediate ferromagnetic layer in the stack of ferromagnetic and insulating layers, a second magnetostrictive layer above the stack of ferromagnetic and insulating layers, and a third electrode electrically coupled to the second magnetostrictive layer. At least one ferromagnetic layer below the intermediate ferromagnetic layer may be switchable between different polarization states responsive to a first voltage applied across the first and second electrodes, and at least one ferromagnetic layer above the intermediate ferromagnetic layer may be switchable between different polarization states responsive to a second voltage applied across the second and third electrodes.
1. An electronic device comprising:
a first electrode;
a first magnetostrictive layer coupled to the first electrode;
a plurality of alternating ferromagnetic and insulating layers stacked above the first magnetostrictive layer;
a second electrode electrically coupled to an intermediate ferromagnetic layer in the stack of ferromagnetic and insulating layers;
a second magnetostrictive layer above the stack of ferromagnetic and insulating layers; and
a third electrode electrically coupled to the second magnetostrictive layer;
at least one ferromagnetic layer below the intermediate ferromagnetic layer being switchable between different polarization states responsive to a first voltage applied across the first and second electrodes, and at least one ferromagnetic layer above the intermediate ferromagnetic layer being switchable between different polarization states responsive to a second voltage applied across the second and third electrodes.
2. The electronic device of claim 1 further comprising:
a first piezoelectric layer below the first magnetostrictive layer; and
a second piezoelectric layer above the second magnetostrictive layer.
3. The electronic device of claim 2 wherein the first and second piezoelectric layers comprise at least one of BaTiO 3 , Ba 0.95 Sr 0.05 TiO 3 , Hf 0.5 Zr 0.5 O 2 , PbTiO 3 , YMnO 3 , BiFeO 3 , Si doped HfO 2 , SrBi 2 TaO 9 , and PbZr x Ti 1-x O 3 .
4. The electronic device of claim 1 wherein the first and second magnetostrictive layers comprise at least one of Co, Fe, NiFe, MnAs, Fe 4 N, MnAl, Co 4 N, LSMO, SrRuO 2 , and CoFeB.
5. The electronic device of claim 1 wherein the ferromagnetic layers comprise at least one of Co, Fe, NiFe, MnAs, Fe 4 N, MnAl, Co 4 N, LSMO, SrRuO 2 , and CoFeB.
6. The electronic device of claim 1 wherein the insulating layers comprise at least one of BaTiO 3 , Ba 0.95 Sr 0.05 TiO 3 , Hf 0.5 Zr 0.5 O 2 , PbTiO 3 , YMnO 3 , BiFeO 3 , Si doped HfO 2 , SrBi 2 TaO 9 , La 0.1 Bi 0.9 MnO 3 , Al 2 O 3 , GaO, GeO, MgO, GaAs, and AlGaAs.
7. The electronic device of claim 1 further comprising a substrate beneath the first magnetostrictive layer.
8. The electronic device of claim 7 wherein the substrate comprises at least one of SrTiO 3 , Si, SmScO 3 , and TbScO 3 .
9. The electronic device of claim 1 comprising electronic circuitry coupled to the first, second and third electrodes for operation as a memory device.
10. The electronic device of claim 9 wherein the memory device comprises a plurality of memory cells, each operable to store sixteen memory states.
11. A memory comprising:
a substrate; and
a plurality of memory cells above the substrate, each memory cell operable to store sixteen memory states and comprising:
a first electrode;
a first magnetostrictive layer coupled to the first electrode;
a plurality of alternating ferromagnetic and insulating layers stacked above the first magnetostrictive layer;
a second electrode electrically coupled to an intermediate ferromagnetic layer in the stack of ferromagnetic and insulating layers;
a second magnetostrictive layer above the stack of ferromagnetic and insulating layers; and
a third electrode electrically coupled to the second magnetostrictive layer;
at least one ferromagnetic layer below the intermediate ferromagnetic layer being switchable between different polarization states responsive to a first voltage applied across the first and second electrodes, and at least one ferromagnetic layer above the intermediate ferromagnetic layer being switchable between different polarization states responsive to a second voltage applied across the second and third electrodes.
12. The memory of claim 11 wherein each memory cell further comprises:
a first piezoelectric layer below the first magnetostrictive layer; and
a second piezoelectric layer above the second magnetostrictive layer.
13. The memory of claim 12 wherein the first and second piezoelectric layers comprise at least one of BaTiO 3 , Ba 0.95 Sr 0.05 TiO 3 , Hf 0.5 Zr 0.5 O 2 , PbTiO 3 , YMnO 3 , BiFeO 3 , Si doped HfO 2 , SrBi 2 TaO 9 , and PbZr x Ti 1-x O 3 .
14. The memory of claim 11 wherein the first and second magnetostrictive layers comprise at least one of Co, Fe, NiFe, MnAs, Fe 4 N, MnAl, CON, LSMO, SrRuO 2 , and CoFeB.
15. The memory of claim 11 wherein the ferromagnetic layers comprise at least one of Co, Fe, NiFe, MnAs, Fe 4 N, MnAl, Co 4 N, LSMO, SrRuO 2 , and CoFeB.
16. The memory of claim 11 wherein the insulating layers comprise at least one of BaTiO 3 , Ba 0.95 Sr 0.05 TiO 3 , Hf 0.5 Zr 0.5 O 2 , PbTiO 3 , YMnO 3 , BiFeO 3 , Si doped HfO 2 , and SrBi 2 TaO 9 .
17. The memory of claim 11 wherein the substrate comprises at least one of SrTiO 3 , Si, SmScO 3 , and TbScO 3 .
18. A method for making an electronic device comprising:
forming a first magnetostrictive layer coupled to a first electrode;
forming a plurality of alternating ferromagnetic and insulating layers stacked above the first magnetostrictive layer;
forming a second electrode electrically coupled to an intermediate ferromagnetic layer in the stack of ferromagnetic and insulating layers;
forming a second magnetostrictive layer above the stack of ferromagnetic and insulating layers; and
forming a third electrode electrically coupled to the second magnetostrictive layer;
at least one ferromagnetic layer below the intermediate ferromagnetic layer being switchable between different polarization states responsive to a first voltage applied across the first and second electrodes, and at least one ferromagnetic layer above the intermediate ferromagnetic layer being switchable between different polarization states responsive to a second voltage applied across the second and third electrodes.
19. The method of claim 18 further comprising:
forming a first piezoelectric layer below the first magnetostrictive layer; and
forming a second piezoelectric layer above the second magnetostrictive layer.
20. The method of claim 19 wherein the first and second piezoelectric layers comprise at least one of BaTiO 3 , Ba 0.95 Sr 0.05 TiO 3 , Hf 0.5 Zr 0.5 O 2 , PbTiO 3 , YMnO 3 , BiFeO 3 , Si doped HfO 2 , SrBi 2 TaO 9 , and PbZr x Ti 1-x O 3 .
21. The method of claim 18 wherein the first and second magnetostrictive layers and the ferromagnetic layers comprise at least one of Co, Fe, NiFe, MnAs, Fe 4 N, MnAl, Co 4 N, LSMO, SrRuO 2 , and CoFeB.
22. The method of claim 18 wherein the insulating layers comprise at least one of BaTio 3 , Ba 0.95 Sr 0.05 TiO 3 , Hf 0.5 Zr 0.5 O 2 , PbTiO 3 , YMnO 3 , BiFeO 3 , Si doped HfO 2 , and SrBi 2 TaO 9 .
23. The method of claim 18 further comprising forming a substrate beneath the first magnetostrictive layer.
24. The method of claim 23 wherein the substrate comprises at least one of SrTiO 3 , Si, SmScO 3 , and TbScO 3 .