Magnetic storage element, magnetic storage device, magnetic memory, and driving method

• US 9,153,340 B2
• Filed: 11/15/2013
• Issued: 10/06/2015
• Est. Priority Date: 11/20/2012
• Status: Active Grant

• Current Assignee: Kioxia Corporation
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Morise, Hirofumi, Fukuzumi, Yoshiaki, Kondo, Tsuyoshi, Nakamura, Shiho, Aochi, Hideaki
• Primary Examiner(s): LE, THONG QUOC
• Application Number:
  US14/081,149
• Publication Number:
  US 20140140126A1
• Time in Patent Office: 690 Days
• Field of Search: 365/158, 365/171, 365/173, 365/80, 365/225.5, 365/88, 365/130, 365/51
• US Class Current: 1/1
• CPC Class Codes: G11C 19/02 using magnetic elements G11C19/14 takes precedence
• CPC Class Codes: G11C 19/08 using thin films in plane structure
• CPC Class Codes: H10B 61/00 Magnetic memory devices, e.g. magnetoresistive RAM [MRAM] devices
• CPC Class Codes: H10B 61/22 of the field-effect transistor [FET] type
• CPC Class Codes: H10N 50/10 Magnetoresistive devices
• CPC Class Codes: H10N 59/00 Integrated devices, or assemblies of multiple devices, comprising at least one galvanomagnetic or Hall-effect element covered by groups H10N50/00 - H10N52/00 MRAM devices H10B61/00

Abstract

A magnetic storage element includes a magnetic nanowire. A cross-section of the magnetic nanowire has first and second visible outlines, the first visible outline has a first minimal point at which a distance from a virtual straight line becomes minimal, a second minimal point at which the distance from the virtual straight line becomes minimal, and a first maximal point at which the distance from the virtual straight line becomes longest between the first minimal point and the second minimal point, and an angle between a first straight line connecting the first minimal point and the second minimal point, and one of a second straight line connecting the first minimal point and the first maximal point and a third straight line connecting the second minimal point and the first maximal point is not smaller than four degrees and not larger than 30 degrees.

Claims

1. A magnetic storage element comprising:

a magnetic nanowire including a magnetic domain and a domain wall;

a pair of electrodes configured to apply current to the magnetic nanowire for shifting the domain wall, the pair of electrodes being connected to the magnetic nanowire, the current flowing in a first direction in which the magnetic nanowire extends;

a writing unit configured to write magnetization information into the magnetic domain, the writing unit being connected to the magnetic nanowire; and

a reading unit configured to read the magnetization information from the magnetic domain, the reading unit being connected to the magnetic nanowire,

wherein

the magnetic nanowire has a magnetization direction perpendicular to the first direction in which the magnetic nanowire extends,

a cross-section of the magnetic nanowire taken along a plane determined by the first direction and a second direction perpendicular to the first direction has first and second visible outlines,

the first visible outline has a first minimal point at which a distance from a virtual straight line parallel to the first direction becomes minimal, a second minimal point at which the distance from the virtual straight line becomes minimal, and a first maximal point at which the distance from the virtual straight line becomes longest between the first minimal point and the second minimal point, the second minimal point being different from the first minimal point, the virtual straight line being located inside the magnetic nanowire, and

an angle between a first straight line connecting the first minimal point and the second minimal point, and one of a second straight line connecting the first minimal point and the first maximal point and a third straight line connecting the second minimal point and the first maximal point is not smaller than four degrees and not larger than 30 degrees.

2. The element according to claim 1, wherein

the second visible outline has a third minimal point at which the distance from the virtual straight line becomes minimal, a fourth minimal point at which the distance from the virtual straight line becomes minimal, and a second maximal point at which the distance from the virtual straight line becomes longest between the third minimal point and the fourth minimal point, the fourth minimal point being different from the third minimal point, and

an angle between a fourth straight line connecting the third minimal point and the fourth minimal point, and one of a fifth straight line connecting the third minimal point and the second maximal point and a sixth straight line connecting the fourth minimal point and the second maximal point is not smaller than four degrees and not larger than 30 degrees.

3. The element according to claim 1, wherein a length of the magnetic nanowire is 60 nm or less in the second direction.

4. The element according to claim 1, wherein

the second visible outline has a second maximal point at which the distance from the virtual straight line becomes longest, the second maximal point corresponding to the first maximal point of the first visible outline, a line connecting the first maximal point and the second maximal point of the second visible outline being substantially perpendicular to the first direction, and

the first and second visible outlines each have a portion located on or outside a circumference of a circle having a diameter that is the line connecting the first maximal point and the second maximal point of the second visible outline.

5. The element according to claim 1, wherein the magnetic domain in the magnetic nanowire has a length of 6 to 200 nm in the first direction.

6. The element according to claim 1, wherein the magnetic nanowire is made of an alloy of a rare-earth element and an iron-group transition element.

7. The element according to claim 1, wherein

the first visible outline has a plurality of minimal points at which the distance from the virtual straight line becomes minimal,

the second visible outline has a plurality of minimal points at which the distance from the virtual straight line becomes minimal, the plurality of minimal points corresponding to the respective minimal points of the first visible outline, the plurality of minimal points being located in corresponding positions in the first direction, and

a distance between adjacent ones of the minimal points of the first visible outline varies with position in the first direction.

8. The element according to claim 1, wherein the magnetic nanowire has a portion with a nanowire width change rate of 10% or higher in a region having a length of 6 nm in the first direction.

9. The element according to claim 1, wherein the magnetic nanowire has a nanowire width change of 10 nm or less in a region having a length of 6 nm in the first direction.

10. A magnetic storage device comprising:

a plurality of magnetic storage elements according to claim 1, the magnetic storage elements being arranged in a matrix form;

a plurality of switching transistors corresponding to the plurality of magnetic storage elements, each of the switching transistors having a source or a drain connected to one end of the reading unit of each corresponding one of the magnetic storage elements in each corresponding column;

a plurality of first interconnects corresponding to rows, gates of the switching transistors in each corresponding row being connected to each of the first interconnects; and

a plurality of second interconnects corresponding to columns, the other end of the reading unit in each of the magnetic storage elements in each corresponding column being connected to each of the second interconnects.

11. A magnetic memory comprising

a plurality of magnetic storage devices according to claim 10, the magnetic storage devices being arranged in a matrix form.

12. A method of driving the magnetic storage element according to claim 1, the method comprising:

applying current to the magnetic nanowire through the pair of electrodes for a first period of time; and

cutting off the current after the applying the current, and standing by for a second period of time, the second period of time being longer than the first period of time.

13. A magnetic storage element comprising:

a magnetic nanowire including a magnetic domain and a domain wall;

a pair of electrodes configured to apply current to the magnetic nanowire for shifting the domain wall, the pair of electrodes being connected to the magnetic nanowire, the current flowing in a first direction in which the magnetic nanowire extends;

a writing unit configured to write magnetization information into the magnetic domain, the writing unit being connected to the magnetic nanowire; and

a reading unit configured to read the magnetization information from the magnetic domain, the reading unit being connected to the magnetic nanowire,

wherein

the magnetic nanowire has a magnetization direction perpendicular to the first direction in which the magnetic nanowire extends,

a cross-section of the magnetic nanowire taken along a plane determined by the first direction and a second direction perpendicular to the first direction has first and second visible outlines,

the first visible outline has a first maximal point at which a distance from a virtual straight line parallel to the first direction becomes maximal, a second maximal point at which the distance from the virtual straight line becomes maximal, and a first minimal point at which the distance from the virtual straight line becomes shortest between the first maximal point and the second maximal point, the second maximal point being different from the first maximal point, the virtual straight line being located inside the magnetic nanowire, and

an angle between a first straight line connecting the first maximal point and the second maximal point, and one of a second straight line connecting the first maximal point and the first minimal point and a third straight line connecting the second maximal point and the first minimal point is not smaller than four degrees and not larger than 30 degrees.

14. The element according to claim 13, wherein

the second visible outline has a third maximal point at which the distance from the virtual straight line becomes maximal, a fourth maximal point at which the distance from the virtual straight line becomes maximal, and a second minimal point at which the distance from the virtual straight line becomes shortest between the third maximal point and the fourth maximal point, the fourth maximal point being different from the third maximal point, and

an angle between a fourth straight line connecting the third maximal point and the fourth maximal point, and one of a fifth straight line connecting the third maximal point and the second minimal point and a sixth straight line connecting the fourth maximal point and the second minimal point is not smaller than four degrees and not larger than 30 degrees.

15. The element according to claim 13, wherein a length of the magnetic nanowire is 60 nm or less in the second direction.

16. The element according to claim 13, wherein

the second visible outline has a second maximal point at which the distance from the virtual straight line becomes longest, the second maximal point corresponding to the first maximal point of the first visible outline, a line connecting the first maximal point and the second maximal point of the second visible outline being substantially perpendicular to the first direction, and

the first and second visible outlines each have a portion located on or outside a circumference of a circle having a diameter that is the line connecting the first maximal point and the second maximal point of the second visible outline.

17. The element according to claim 13, wherein the magnetic domain in the magnetic nanowire has a length of 6 to 200 nm in the first direction.

18. The element according to claim 13, wherein the magnetic nanowire is made of an alloy of a rare-earth element and an iron-group transition element.

19. The element according to claim 13, wherein

the first visible outline has a plurality of minimal points at which the distance from the virtual straight line becomes minimal,

the second visible outline has a plurality of minimal points at which the distance from the virtual straight line becomes minimal, the plurality of minimal points corresponding to the respective minimal points of the first visible outline, the plurality of minimal points being located in corresponding positions in the first direction, and

a distance between adjacent ones of the minimal points of the first visible outline varies with position in the first direction.

20. The element according to claim 13, wherein the magnetic nanowire has a portion with a nanowire width change rate of 10% or higher in a region having a length of 6 nm in the first direction.

21. The element according to claim 13, wherein the magnetic nanowire has a nanowire width change of 10 nm or less in a region having a length of 6 nm in the first direction.

22. A magnetic storage device comprising:

a plurality of magnetic storage elements according to claim 13, the magnetic storage elements being arranged in a matrix form;

a plurality of switching transistors corresponding to the plurality of magnetic storage elements, each of the switching transistors having a source or a drain connected to one end of the reading unit of each corresponding one of the magnetic storage elements in each corresponding column;

a plurality of first interconnects corresponding to rows, gates of the switching transistors in each corresponding row being connected to each of the first interconnects; and

a plurality of second interconnects corresponding to columns, the other end of the reading unit in each of the magnetic storage elements in each corresponding column being connected to each of the second interconnects.

23. A magnetic memory comprising

a plurality of magnetic storage devices according to claim 22, the magnetic storage devices being arranged in a matrix form.