Multi-bit magnetic memory with independently programmable free layer domains

• US 8,279,662 B2
• Filed: 11/11/2010
• Issued: 10/02/2012
• Est. Priority Date: 11/11/2010
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Lou, Xiaohua, Gao, Zheng, Dimitrov, Dimitar V.
• Primary Examiner(s): Sofocleous, Alexander
• Assistant Examiner(s): Byrne, Harry W
• Application Number:
  US12/944,523
• Publication Number:
  US 20120120718A1
• Time in Patent Office: 691 Days
• Field of Search: 365/48, 365/55, 365/62, 365/66, 365/74, 365/78, 365 80- 93, 365/100, 365/130, 365/131, 365/148, 365/158, 365171-173, 365/209, 365/213, 365/225.5, 365/230.07, 365/232, 365/243.5, 216/22, 257/295, 257/421, 257/E21.665, 438/3, 428810-816, 428817-8251, 428/826, 977933-935
• US Class Current: 365/158
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: G11C 11/5607 using magnetic storage elements

Abstract

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 magnetic tunnel junction (MTJ) has a ferromagnetic free layer with multiple magnetic domains that are each independently programmable to predetermined magnetizations. Those magnetizations can then be read as different logical states of the MTJ.

Claims

1. A memory cell comprising a magnetic tunnel junction (MTJ) with a ferromagnetic free layer having multiple magnetic domains that are each independently programmable to predetermined magnetizations that are read as logical states of the MTJ.

2. The memory cell of claim 1, wherein a first domain is present in a first region of the free layer that is wider than a second region in which a second domain is present.

3. The memory cell of claim 2, wherein the first and second regions hold independent magnetic domains due to shape anisotropy.

4. The memory cell of claim 2, wherein the first region has a first width that transitions to a second width of the second region with a right angle notch.

5. The memory cell of claim 2, wherein the first region has a first width that transitions to a second width of the second region with a continuously curvilinear sidewall.

6. The memory cell of claim 1, wherein the MTJ has a pinned layer and tunnel junction have a width that is the same as a region of the free layer.

7. The memory cell of claim 2, wherein the first region has a magnetic coercivity that is less than the second region.

8. The memory cell of claim 1, wherein different predetermined magnetizations are programmed to the domains with different programming currents.

9. The memory cell of claim 2, wherein the first and second regions are laterally adjacent and each contact a tunnel junction layer.

10. The memory cell of claim 1, wherein the magnetic domains are read as resistances in parallel.

11. The memory cell of claim 2, wherein the first and second regions have continuously curvilinear sidewalls.