Spin-transfer torque magnetic random access memory (STTMRAM) with perpendicular laminated free layer
View Patent ↗A perpendicular spin-transfer torque magnetic random access memory (STTMRAM) element includes a fixed layer having a magnetization that is substantially fixed in one direction and a barrier layer formed on top of the fixed layer and a free layer. The free layer has a number of alternating laminates, each laminate being made of a magnetic layer and an insulating layer. The magnetic layer is switchable and formed on top of the barrier layer. The free layer is capable of switching its magnetization to a parallel or an anti-parallel state relative to the magnetization of the fixed layer during a write operation when bidirectional electric current is applied across the STTMRAM element. Magnetic layers of the laminates are ferromagnetically coupled to switch together as a single domain during the write operation and the magnetization of the fixed and free layers and the magnetic layers of the laminates have perpendicular anisotropy.
1. A spin-transfer torque magnetic random access memory (STTMRAM) element comprising:
a magnetic fixed layer having an invariable magnetization direction perpendicular to layer plane thereof;
a barrier layer formed adjacent to said magnetic fixed layer; and
a magnetic free layer formed adjacent to said barrier layer opposite said magnetic fixed layer, said magnetic free layer having a variable magnetization direction perpendicular to layer plane thereof and including a first plurality of magnetic sublayers interleaved with a second plurality of insulating sublayers.
2. The STTMRAM element of claim 1 , wherein said magnetic fixed layer comprises two magnetic sublayers having said invariable magnetization direction.
3. The STTMRAM element of claim 2 , wherein at least one of said two magnetic sublayers of said magnetic fixed layer comprises cobalt, iron, and boron.
4. The STTMRAM element of claim 2 , wherein at least one of said two magnetic sublayers of said magnetic fixed layer comprises iron and platinum.
5. The STTMRAM element of claim 2 , wherein each of said two magnetic sublayers of said magnetic fixed layer comprises cobalt and iron.
6. The STTMRAM element of claim 2 , wherein at least one of said two magnetic sublayers of said magnetic fixed layer has a multilayer structure formed by interleaving layers of a first material with layers of a second material with at least one of said first and second materials being magnetic.
7. The STTMRAM element of claim 6 , wherein said multilayer structure is made of [Co/Pt], [Co/Pd], [Co/Ni], [CoFe/Pt], or any combination thereof.
8. The STTMRAM element of claim 1 , wherein at least one of said first plurality of magnetic sublayers comprises cobalt, iron, and boron.
9. The STTMRAM element of claim 1 , wherein each of said first plurality of magnetic sublayers comprises cobalt and iron.
10. The STTMRAM element of claim 1 , wherein each of said second plurality of insulating sublayers is made of an oxide.
11. The STTMRAM element of claim 1 , wherein each of said second plurality of insulating sublayers comprises magnesium and oxygen.
12. The STTMRAM element of claim 11 , wherein each of said first plurality of magnetic sublayers comprises cobalt, iron, and boron.
13. The STTMRAM element of claim 1 , wherein at least one of said second plurality of insulating sublayers comprises magnesium and oxygen.
14. The STTMRAM element of claim 1 , further comprising a non-magnetic seed or cap layer formed adjacent to said magnetic free layer.
15. The STTMRAM element of claim 1 , wherein said first plurality of magnetic sublayers are ferromagnetically coupled.