Magnetic memory
According to one embodiment, a device includes a member including a first portion having a first dimension in first direction, a second portion spaced from the first portion and having a second dimension in the first direction, a third portion between the first and second portions and having a third dimension in the first direction, and a fourth portion between the first and third portions and having a fourth dimension in the first direction; and a circuit to supply a shift pulse including first and second pulses to the member and move a domain wall in the member. The third dimension is less than the first dimension. The second and fourth dimensions are less than the third dimension. A second value of the second pulse is less than a first value of the first pulse.
1. A magnetic memory comprising:
a magnetic member including a first portion with a first dimension in a first direction, a second portion spaced from the first portion in a second direction crossing the first direction and having a second dimension in the first direction, a third portion provided between the first portion and the second portion and having a third dimension in the first direction, and a fourth portion provided between the first portion and the third portion and having a fourth dimension in the first direction; and
a circuit configured to supply a shift pulse including a first pulse and a second pulse to the magnetic member, and to move a domain wall in the magnetic member in the second direction,
wherein
the third dimension is less than the first dimension, and the second dimension and the fourth dimension is less than the third dimension, and
the first pulse has a first current value, and the second pulse has a second current value which is less than the first current value.
2. The magnetic memory of claim 1 , wherein
the second pulse is supplied to the magnetic member after the first pulse is supplied to the magnetic member.
3. The magnetic memory of claim 1 , wherein
the first pulse moves the domain wall from the first portion toward the second portion, and
the second pulse moves the domain wall in the fourth portion into the second portion.
4. The magnetic memory of claim 1 , wherein
the shift pulse includes a first period between the first pulse and the second pulse.
5. The magnetic memory of claim 4 , wherein
the shift pulse has, during the first period, a third current value which is less than a threshold for moving the domain wall.
6. The magnetic memory of claim 1 , wherein
the first pulse has the first current value during a first period from a first time instant to a second time instant, and
the second pulse has the second current value during a second period from the second time instant to a third time instant.
7. The magnetic memory of claim 1 , wherein
a first pulse width of the first pulse is equal to a second pulse width of the second pulse.
8. The magnetic memory of claim 1 , wherein
the magnetic member is provided above a substrate,
the first direction is a direction along a surface of the substrate, and
the second direction is a direction crossing the surface of the substrate.
9. The magnetic memory of claim 1 , wherein
the magnetic member is provided above a substrate, and
each of the first direction and the second direction is a direction along a surface of the substrate.
10. The magnetic memory of claim 1 , wherein
the magnetic member has a cylindrical structure.
11. The magnetic memory of claim 1 , wherein
the magnetic member has a plate-shaped structure.
12. The magnetic memory of claim 1 , wherein
the magnetic member has a constriction structure.
13. The magnetic memory of claim 1 , wherein
a first volume of the first portion is greater than a second volume of the third portion.
14. The magnetic memory of claim 1 , wherein
the first current value has a magnitude for the domain wall to move into the fourth portion via the first portion, and
the second current value is less than the first current value and has a magnitude for the domain wall to move from the fourth portion into the second portion via the third portion.
15. The magnetic memory of claim 1 , wherein
the first current value and the second current value have a relationship:
ia>A L Jc>ib>A S Jc
where ia is the first current value,
ib is the second current value,
Jc is a current density of a threshold current for moving the domain wall,
A L is a maximum value of a cross-sectional area of the first portion, and
A S is a maximum value of a cross-sectional area of the third portion.
16. A magnetic memory comprising:
a magnetic member including a first portion with a first dimension in a first direction, a second portion spaced from the first portion in a second direction crossing the first direction and having a second dimension in the first direction, a third portion provided between the first portion and the second portion and having a third dimension in the first direction, and a fourth portion provided between the first portion and the third portion and having a fourth dimension in the first direction; and
a circuit configured to supply a shift pulse including a first pulse and a second pulse to the magnetic member, and to move a domain wall in the magnetic member in the second direction,
wherein
a first current value of the first pulse and a second current value of the second pulse have a relationship:
ia>A L Jc>ib>A S Jc
where ia is the first current value,
ib is the second current value,
Jc is a current density of a threshold current for moving the domain wall,
A L is a maximum value of a cross-sectional area of the first portion, and
A S is a maximum value of a cross-sectional area of the third portion.
17. The magnetic memory of claim 16 , wherein
the third dimension is less than the first dimension, and each of the second dimension and the fourth dimension is less than the third dimension.
18. The magnetic memory of claim 16 , wherein
the second pulse is supplied to the magnetic member after the first pulse is supplied to the magnetic member.
19. The magnetic memory of claim 16 , wherein
a first volume of the first portion is greater than a second volume of the third portion.