1. A magnetic random access memory (MRAM) comprising:
a generally planar substrate;
a plurality of first and second electrically conductive lines on the substrate, the second lines being located between the substrate and the first lines with the first lines overlapping the second lines and spaced from the second lines in a generally perpendicular direction from the substrate to define a plurality of intersection regions, the first line and second line at each intersection region being generally orthogonal wherein each of the first lines comprises a pair of coplanar spaced lines lying in a plane substantially parallel to the substrate, each of the second lines comprises a pair of coplanar spaced lines lying in a plane substantially parallel to the substrate, and the region between the overlapping pairs of coplanar lines is an intersection region; and
a plurality of memory stacks, each memory stack located in an intersection region and comprising (a) a first memory cell having a pinned ferromagnetic layer, a free ferromagnetic layer with an in-plane easy axis of magnetization aligned generally parallel with one of said first and second lines, and a nonmagnetic coupling layer between the pinned and free layers, (b) a second memory cell having a pinned ferromagnetic layer, a free ferromagnetic layer with an in-plane easy axis of magnetization aligned substantially nonparallel with the easy axis of magnetization of the free layer of the first cell, and a nonmagnetic coupling layer between the pinned and free layers, and (c) a nonmagnetic separation layer between said two memory cells.
2. The MRAM of claim 1 wherein the substrate is parallel to the X-Y plane of an X-Y-Z coordinate system and a direction perpendicular to the substrate is parallel to the Z axis, wherein the first lines are mutually parallel and parallel to the X axis, the second lines are mutually parallel and parallel to the Y axis, and the memory cells in each memory stack are stacked parallel to the Z axis.
3. The MRAM of claim 1 wherein each of the memory cells is a magnetic tunnel junction (MTJ) cell and wherein each nonmagnetic coupling layer is a tunnel barrier.
4. The MRAM of claim 1 wherein each memory cell has an electrical resistance difference \u0394R between the parallel and antiparallel alignment of its free and pinned layer magnetization directions, and wherein the \u0394R of the first memory cell is substantially different from the \u0394R of the second memory cell.
5. The MRAM of claim 4 wherein each memory cell is a magnetic tunnel junction (MTJ) cell and each nonmagnetic coupling layer is a tunnel barrier, and wherein the tunnel barrier thickness of the first MTJ cell is substantially different from the tunnel barrier thickness of the second MTJ cell.
6. The MRAM of claim 1 wherein the easy axes of magnetization of the free layers of the first and second cells in each memory stack are aligned substantially orthogonal to each other.
7. The MRAM of claim 1 wherein the easy axis of magnetization of the free layer in each cell is the axis of anisotropy induced by the shape of the cell.
8. The MRAM of claim 1 wherein the easy axis of magnetization of the free layer in each cell is the axis of anisotropy induced during deposition of the free layer, and wherein the first and second cells have the same shape and matching perimeters.
9. The MRAM of claim 8 wherein the memory cells have a circular shape.
10. The MRAM of claim 1 wherein the pinned layer in each memory cell is an AP-pinned layer.
11. The MRAM of claim 1 further comprising a plurality of transistors between the substrate and the second lines, and wherein each memory stack is electrically connected to a transistor.
12. The MRAM of claim 11 further comprising circuitry coupled to the transistors for detecting the electrical resistance across the memory stacks.
13. The MRAM of claim 1 further comprising write circuitry for directing electrical current bidirectionally to the first and second lines.
14. A magnetic random access memory (MRAM) comprising:
a substrate parallel to an X-Y plane of an X-Y-Z coordinate system;
a plurality of memory units on the substrate and aligned parallel to the Z axis, each memory unit comprising (a) a first magnetic tunnel junction (MTJ) cell having a free ferromagnetic layer with an easy axis of magnetization aligned in an X-Y plane generally parallel to one of said X and Y axes, (b) a second magnetic tunnel junction (MTJ) cell having a free ferromagnetic layer with an easy axis of magnetization aligned in an X-Y plane at an angle substantially orthogonal to the easy axis of magnetization of the free layer of the first cell, and (c) a nonmagnetic separation layer between said first and second cells;
a plurality of first pairs of electrically conductive coplanar spaced lines lying in an X-Y plane and substantially parallel to the X axis;
a plurality of second pairs of electrically conductive coplanar spaced lines lying in an X-Y plane and substantially parallel to the Y axis, each memory unit being located between the first and second pairs of lines; and
write circuitry coupled to the first and second pairs of lines for directing electrical current to the first and second pairs of lines.
15. The MRAM of claim 14 wherein the easy axis of magnetization of the free layer in each cell is the axis of anisotropy induced by the shape of the cell.
16. The MRAM of claim 14 wherein the easy axis of magnetization of the free layer in each cell is the axis of anisotropy induced during deposition of the free layer, and wherein the first and second cells have the same shape and matching perimeters.
17. The MRAM of claim 14 wherein each cell has an electrical resistance difference \u0394R between two antiparallel orientations of its free layer magnetization, and wherein the \u0394R of the first cell is substantially different from the \u0394R of the second cell.
18. The MRAM of claim 14 further comprising a plurality of transistors on the substrate, and wherein each memory unit is electrically connected to a transistor.
19. The MRAM of claim 18 further comprising read circuitry coupled to the transistors for detecting the electrical resistance across the memory units.
20. The MRAM of claim 17 wherein the write circuitry provides bidirectional current on the first and second lines.
21. A method for writing simultaneously a pair of magnetic tunnel junction (MTJ) memory cells on a the substrate of a magnetic random access memory (MRAM), the MRAM substrate being parallel to an X-Y plane of an X-Y-Z coordinate system, the MRAM having X and Y electrically conductive write lines and the pair of memory cells being in a stack extending from the substrate along the Z axis, the stack comprising a first MTJ cell having a free ferromagnetic layer with an easy axis of magnetization aligned in an X-Y plane generally parallel to the Y axis, a second MTJ cell having a free ferromagnetic layer with an easy axis of magnetization aligned in an X-Y plane generally parallel to the X axis the first and second MTJ cells having substantially the same anisotropy field between Hk(MIN) and Hk(MAX), and a nonmagnetic separation layer between said first and second MTJ cells, the method comprising:
applying in the X write line an electrical write-current pulse having a magnitude to generate a magnetic field less than Hk(MIN) and simultaneously applying in the Y write line an electrical write-current pulse of substantially the same magnitude, the write-current pulse magnitude being selected such that the composite magnetic field in the presence of both write-current pulses at an angle approximately 45 degrees between the X and Y axes is greater than Hk(MAXV); and
prior to applying the simultaneous write-current pulses, selecting the current direction in the X and Y write lines to thereby select one of four magnetic states for the pair of MTJ cells.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An adjustable door sill assembly comprising:
a threshold;
a threshold cap on the threshold and having at least one opening formed therein;
a carriage beneath the threshold cap and positioned proximate the at least one opening;
at least one adjustment element on the carriage capable of causing the threshold cap to move vertically with respect to the threshold, the adjustment element being accessible through the opening on the threshold cap; and
a cap plug for covering the opening, the cap plug being removably attachable with the carriage.
2. The adjustable door sill assembly of claim 1, wherein the cap plug has a protrusion with a shoulder thereon, and the carriage has a receiving portion with a projection, whereby the shoulder and the projection cooperate to removably attach the cap plug to the carriage.
3. The adjustable door sill assembly of claim 1, wherein the projection is positioned circumferentially around the receiving portion of the carriage.
4. The adjustable door sill assembly of claim 1, wherein the carriage has a means for retaining the cap plug therein.
5. The adjustable door sill assembly of claim 1, wherein the threshold cap further comprises a channel formed by at least two legs extending downwardly from the threshold cap, the carriage being snap-fit within the channel.
6. The adjustable door sill assembly of claim 1, wherein the threshold cap has a plurality of openings, the carriage is selectively positionable under any one of the plurality of openings.
7. The adjustable door sill assembly of claim 1, wherein the threshold cap has a length shorter than the length of the adjustable door sill assembly, the threshold cap and the carriage are selectively positionable along the adjustable door sill assembly.
8. A carriage, for use with a threshold cap having one or more openings, a sill, and a cap plug, the carriage comprising:
a housing capable of being positionable under the threshold cap and on top at least a portion of the sill;
the housing having an opening to receive and retain the cap plug; and
the housing being operably connected to the threshold cap such that the threshold cap is vertically adjustable.
9. The carriage of claim 8, wherein the housing further comprises a receiving portion with a projection, the projection operably engages the cap plug to allow the cap plug to be removably attached with the housing.
10. The carriage of claim 8, wherein the projection is positioned circumferentially around the receiving portion of the housing.
11. The carriage of claim 8, wherein the receiving portion comprises one or more projections, the one or more projections operably engages the cap plug to allow the cap plug to be removably attached with the housing.
12. The carriage of claim 8, the housing having a means for retaining a cap plug therein.
13. The carriage of claim 8, wherein the opening extends through the housing, the opening capable of receiving an adjustable element is opposite the cap plug, the opening providing access to the adjustment element when the cap plug is not in the opening.
14. The carriage of claim 8, wherein the opening has a lower portion, the lower portion capable of matingly receiving the adjustment element.
15. The carriage of claim 14, wherein the lower portion is capable of fixably and removably receiving the adjustment element.
16. An adjustable door sill assembly capable of being adjusted to form a seal with the bottom of the door, the adjustable door sill assembly comprising:
a. a threshold;
b. a threshold cap on the threshold and having at least one opening;
c. a carriage beneath the threshold cap and positioned proximate the at least one opening and connected to the threshold cap;
d. at least one adjustment element on the carriage capable of causing the threshold cap to move vertically with respect to the threshold, the adjustment element being accessible through the at least one opening on the threshold cap; and
e. a cap plug for covering the at least one opening, the carriage comprising a means for retaining the cap plug in the carriage.
17. The adjustable door sill assembly of claim 15, wherein the cap plug has a protrusion with a shoulder thereon, and the carriage has a receiving portion with a projection, whereby the shoulder and the projection cooperate to removable attach the cap plug to the carriage.
18. The adjustable door sill assembly of claim 15, wherein the threshold cap further comprises a channel formed by at least two legs extending downwardly from a top of the threshold cap, the carriage being retained within the channel.
19. The adjustable door sill assembly of claim 15, wherein threshold cap has a plurality of openings, the carriage is selectively positionable under any one of the plurality of openings.
20. The adjustable door sill assembly of claim 15, wherein the threshold cap has a length shorter than the length of the adjustable door sill assembly, the threshold cap and the carriage are selectively positionable along the adjustable door sill assembly.
21. The adjustable door sill assembly of claim 15, wherein the projection is positioned circumferentially around the receiving portion of the housing.
22. A door sill assembly comprising;
a. a threshold having a deck;
b. a channel extending along the threshold;
c. a threshold cap disposed in the channel and having an opening formed therethrough;
d. a carriage disposed beneath the threshold cap aligned with the opening; and
e. a plug having a head sized to cover the opening and a protrusion sized and configured to extend through the opening and attach releasably to the carriage.
23. The door sill assembly of claim 22, wherein the protrusion has a shoulder thereon, and the carriage has a receiving portion with a projection, whereby the shoulder and the projection cooperate to removably attach the plug to the carriage.
24. The door sill assembly of claim 23, wherein the projection is positioned circumferentially around the receiving portion of the carriage.
25. The door sill assembly of claim 22, wherein the carriage has a means for retaining the cap plug therein.
26. The door sill assembly of claim 22, wherein the threshold cap further comprises a channel formed by at least two legs extending downwardly from a top of the threshold cap, the carriage being snap-fit within the channel.
27. The door sill assembly of claim 22, wherein the threshold cap has a plurality of openings, the carriage is selectively positionable under any one of the plurality of openings.
28. The door sill assembly of claim 22, wherein the threshold cap has a length shorter than the length of the door sill assembly, the threshold cap and the carriage are selectively positionable along the door sill assembly.