Voltage-switched magnetic random access memory (MRAM) and method for using the same

1. A magnetic random access memory (MRAM) element comprising:

a first magnetic tunnel junction (MTJ) including a first magnetic reference layer and a first magnetic free layer with a first insulating tunnel junction layer interposed therebetween, said first magnetic reference layer having a first pseudo-fixed magnetization direction substantially perpendicular to a layer plane thereof, said first magnetic free layer having a first variable magnetization direction substantially perpendicular to a layer plane thereof;

a second MTJ including a second magnetic reference layer and a second magnetic free layer with a second insulating tunnel junction layer interposed therebetween, said second magnetic reference layer having a second pseudo-fixed magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first pseudo-fixed magnetization direction, said second magnetic free layer having a second variable magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first variable magnetization direction; and

an anti-ferromagnetic coupling layer that couples said first and second magnetic free layers to each other.

2. The MRAM element of claim 1 , wherein said first magnetic free layer has a first magnetic moment, said second magnetic free layer has a second magnetic moment substantially smaller than said first magnetic moment.

3. The MRAM element of claim 1 , further comprising a first contact formed adjacent to said first magnetic reference layer opposite said first insulating tunnel junction layer and a second contact formed adjacent to said second magnetic reference layer opposite said second insulating tunnel junction layer.

4. The MRAM element of claim 1 , wherein said first and second magnetic free layers each is made of an alloy comprising cobalt, iron, and boron.

5. The MRAM element of claim 1 , wherein said first and second magnetic free layers each comprises two magnetic sublayers with a tantalum sublayer interposed therebetween.

6. The MRAM element of claim 1 , wherein said first and second magnetic reference layers each is made of an alloy comprising cobalt, iron, and boron.

7. The MRAM element of claim 1 , wherein said first and second magnetic reference layers each has a multilayer structure formed by interleaving two different types of materials with at least one of said two different types of materials being magnetic.

8. The MRAM element of claim 1 , wherein said anti-ferromagnetic coupling layer is made of ruthenium or tantalum.

9. The MRAM element of claim 1 , wherein each of said first and second insulating tunnel junction layers is made of magnesium oxide or aluminum oxide.

10. The MRAM element of claim 1 , wherein each of said first and second insulating tunnel junction layers has an RA value in the range of about 20 to 2000 Ω·μm 2 .

11. The MRAM element of claim 1 , further comprising a first anti-ferromagnetic layer formed adjacent to said first magnetic reference layer opposite said first insulating tunnel junction layer.

12. The MRAM element of claim 11 , further comprising a second anti-ferromagnetic layer formed adjacent to said second magnetic reference layer opposite said second insulating tunnel junction layer.

13. The MRAM element of claim 1 , wherein said first magnetic reference layer has a first pseudo-fixed magnetization direction substantially perpendicular to a layer plane thereof, said second magnetic reference layer has a second pseudo-fixed magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first pseudo-fixed magnetization direction, said first magnetic free layer has a first variable magnetization direction substantially perpendicular to a layer plane thereof, said second magnetic free layer has a second variable magnetization direction that is substantially perpendicular to a layer plane thereof and is substantially opposite to said first variable magnetization direction, said first magnetic free layer has a first magnetic moment, said second magnetic layer has a second magnetic moment substantially smaller than said first magnetic moment.

14. The MRAM element of claim 13 , further comprising a first contact formed adjacent to said first magnetic reference layer opposite said first insulating tunnel junction layer and a second contact formed adjacent to said second magnetic reference layer opposite said second insulating tunnel junction layer.

15. A method for switching the MRAM element of claim 14 from low to high resistance state, comprising the steps of:

applying an electric potential with a positive terminal electrically connected to said second contact and a negative terminal electrically connected to said first contact; and

removing said electric potential.

16. A method for switching the MRAM element of claim 14 from high to low resistance state, comprising the steps of:

applying an electric potential with a positive terminal electrically connected to said first contact and a negative terminal electrically connected to said second contact; and

removing said electric potential.