Magnetic structure with multilayered seed
The present invention is directed to an MTJ memory element, which comprises a magnetic fixed layer structure formed on top of a seed layer structure that includes a first seed layer and a second seed layer. The first seed layer includes one or more layers of nickel interleaved with one or more layers of a transition metal, which may be tantalum, titanium, or vanadium. The second seed layer is made of an alloy or compound comprising nickel and another transition metal, which may be chromium, tantalum, or titanium. The magnetic fixed layer structure has a first invariable magnetization direction substantially perpendicular to a layer plane thereof and includes layers of a first type material interleaved with layers of a second type material with at least one of the first and second type materials being magnetic. The first and second type materials may be cobalt and nickel, respectively.
1. A magnetic structure comprising:
a seed layer structure including a first seed layer and a second seed layer, said first seed layer including one or more layers of a first transition metal interleaved with one or more layers of a second transition metal, said second seed layer is made of an alloy comprising said first transition metal and a third transition metal; and
a magnetic fixed layer structure formed adjacent to said first seed layer and having a first invariable magnetization direction substantially perpendicular to a layer plane thereof, said magnetic fixed layer structure including layers of a first type material interleaved with layers of a second type material with at least one of said first and second type materials being magnetic.
2. The magnetic structure of claim 1 , wherein said first transition metal is nickel.
3. The magnetic structure of claim 1 , wherein said first transition metal is cobalt.
4. The magnetic structure of claim 1 , wherein said second transition metal is tantalum.
5. The magnetic structure of claim 1 , wherein said second transition metal is titanium or vanadium.
6. The magnetic structure of claim 1 , wherein said third transition metal is chromium.
7. The magnetic structure of claim 1 , wherein said third transition metal is tantalum or titanium.
8. The magnetic structure of claim 1 , wherein said first and second type materials are cobalt and nickel, respectively.
9. The magnetic structure of claim 1 , wherein said first and second type materials are cobalt and platinum, respectively.
10. The magnetic structure of claim 1 , wherein said first seed layer is non-magnetic.
11. The magnetic structure of claim 1 , wherein said second seed layer is non-magnetic.
12. The magnetic structure of claim 1 , wherein said magnetic fixed layer structure includes a first magnetic fixed layer and a second magnetic fixed layer with a first perpendicular enhancement layer (PEL) interposed therebetween, each of said first and second magnetic fixed layers includes one or more layers of the first type material interleaved with one or more layers of the second type material.
13. The magnetic structure of claim 12 , wherein said first PEL is made of chromium.
14. The magnetic structure of claim 12 , wherein said first and second type materials are cobalt and nickel, respectively.
15. The magnetic structure of claim 1 further comprising:
an anti-ferromagnetic coupling layer formed adjacent to said magnetic fixed layer structure opposite said first seed layer; and
a magnetic reference layer structure formed adjacent to said anti-ferromagnetic coupling layer, said magnetic reference layer structure having a second invariable magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first invariable magnetization direction,
wherein said magnetic reference layer structure includes a first magnetic reference layer and a second magnetic reference layer with a second perpendicular enhancement layer (PEL) interposed therebetween, said second magnetic reference layer formed adjacent to said anti-ferromagnetic coupling layer opposite said magnetic fixed layer structure and including one or more layers of a third type material interleaved with one or more layers of a fourth type material with at least one of said third and fourth type materials being magnetic.
16. The magnetic structure of claim 15 , wherein said third and fourth type materials are cobalt and nickel, respectively.
17. The magnetic structure of claim 15 , wherein said third and fourth type materials are cobalt and platinum, respectively.
18. The magnetic structure of claim 15 further comprising:
an insulating tunnel junction layer formed adjacent to said first magnetic reference layer; and
a magnetic free layer structure formed adjacent to said insulating tunnel junction layer and including one or more magnetic free layers that have a variable magnetization direction substantially perpendicular to layer planes thereof.
19. The magnetic structure of claim 18 , wherein said magnetic free layer structure includes a first magnetic free layer and a second magnetic free layer with a third perpendicular enhancement layer (PEL) interposed therebetween.