Flux programmed multi-bit magnetic memory
View Patent ↗An apparatus and associated method for a non-volatile memory cell, such as a multi-bit magnetic random access memory cell. In accordance with various embodiments, a first magnetic tunnel junction (MTJ) is adjacent to a second MTJ having a magnetic filter. The first MTJ is programmed to a first logical state with a first magnetic flux while the magnetic filter absorbs the first magnetic flux to prevent the second MTJ from being programmed.
1. A memory cell comprising a first magnetic tunnel junction (MTJ) adjacent a second MTJ having a magnetic filter, the first MTJ being programmed to a first logical state with a first magnetic flux while the magnetic filter absorbs the first magnetic flux to prevent the second MTJ from being programmed.
2. The memory cell of claim 1 , wherein the absorption of the first magnetic flux saturates the magnetic filter and induces a transition from magnetically insulative to conductive.
3. The memory cell of claim 1 , wherein the first and second MTJs are concurrently programmed by a second magnetic flux that is greater than a predetermined valued.
4. The memory cell of claim 3 , wherein the first magnetic flux is below the predetermined value.
5. The memory cell of claim 1 , wherein the magnetic flux is generated by current passing through a word line that is noncontactingly adjacent to the MTJs.
6. The memory cell of claim 5 , wherein the first and second MTJs each extend along a long axis that is perpendicular to the flow of current along the word line.
7. The memory cell of claim 1 , wherein the magnetic filter is a soft magnetic material that has a low coercivity.
8. The memory cell of claim 1 , wherein the first and second MTJs are each coupled to a read line on a top surface and a source plane on a bottom surface.
9. The memory cell of claim 8 , wherein the source plane is connected to a selection device that selectively allows reading of the first and second MTJs.
10. The memory cell of claim 1 , wherein the first MTJ has a different resistance than the second MTJ.
11. The memory cell of claim 10 , wherein the first MTJ has a greater resistance than the second MTJ due to a tunnel junction of the first MTJ having a greater thickness than a tunnel junction of the second MTJ.
12. A method comprising:
providing a first magnetic tunnel junction (MTJ) adjacent a second MTJ having a magnetic filter; and
programming a first logical state to the first MTJ with a first magnetic flux while the magnetic filter absorbs the first magnetic flux to prevent the second MTJ from being programmed.
13. The method of claim 12 , wherein the magnetic flux is generated by a current flowing through a word line that is noncontactingly adjacent the first and second MTJs.
14. The method of claim 12 , wherein the magnetic flux is less than a predetermined threshold value.
15. The method of claim 12 , wherein a second magnetic flux greater than a predetermined threshold value saturates the magnetic filter and programs the first and second MTJs.
16. The method of claim 15 , wherein the first magnetic flux flows in a first direction and the second magnetic flux flows in an opposite second direction.
17. The method of claim 15 , wherein the first and second MTJs are programmed to opposite magnetizations with successive passage of the second then first magnetic fluxes.
18. The method of claim 12 , wherein the first and second MTJs are coupled to a source plane that is connected to a selection device that selectively allows concurrent reading of the MTJs.
19. A memory cell comprising:
a first magnetic tunnel junction (MTJ) having a magnetically conductive spacer adjacent a second MTJ having a magnetic filter, the conductive spacer and magnetic filter each attached to a top surface of each MTJ and a read line;
a word line separated from the first and second MTJs by the read line, the first MTJ being programmed to a first logical state with a first magnetic flux generated by a first current below a predetermined value passing through the word line while the magnetic filter absorbs the first magnetic flux to prevent the second MTJ from being programmed.
20. The memory cell of claim 19 , wherein the first and second MTJs are programmed to opposite logical states by passing a second current above the predetermined threshold value through the word line to generate a second magnetic flux that programs both MTJs then passing the first current through the word line.