Magnetic memory element, method of driving same, and nonvolatile storage device
View Patent ↗In order to obtain a memory cell of size 4 F 2 to realize cross-point type memory, a magnetic memory element is used having a spin valve structure including a free layer 5 , nonmagnetic layer 4 , and layer 3 . The layer or the free layer includes an N-type ferrimagnetic material, and the magnetic compensation point of the N-type ferrimagnetic material is lower than the temperature reached by the layer when a certain write pulse is applied to control the combination of magnetizations of the free layer and layer, and higher than the temperature reached by the layer when another write pulse is applied. These write pulses can have the same polarity.
1. A magnetic memory element, comprising:
a spin valve structure having a free layer, a nonmagnetic layer, and a pinned layer, the pinned layer and the free layer sandwiching the nonmagnetic layer, such that information is recordable therein by applying an electric pulse across the free layer and the pinned layer, wherein
a selected one of the pinned layer and the free layer includes a ferrimagnetic layer made of an N-type ferrimagnetic material, a magnetic compensation point Tcomp of the N-type ferrimagnetic material being in a storage retention operation temperature range of the magnetic memory element.
2. The magnetic memory element according to claim 1 , wherein the selected layer further includes a supplemental magnetic layer made of a magnetic material,
the magnetic material has a temperature dependence of magnetization that is smaller than a temperature dependence of magnetization of the N-type ferrimagnetic layer, and
the supplemental magnetic layer being formed on the nonmagnetic layer side of the selected layer.
3. The magnetic memory element according to claim 1 , further comprising a metal layer containing magnesium or aluminum, provided between the nonmagnetic layer and the selected layer.
4. The magnetic memory element according to claim 1 , further comprising a current-constricting structure disposed near one of two faces defining a thickness of the selected layer, and on a side opposite to the nonmagnetic layer.
5. The magnetic memory element according to claim 1 , wherein an orientation of magnetization of the free layer changes with an increase in temperature from an in-plane direction perpendicular to a film plane of the free layer.
6. The magnetic memory element according to claim 5 , wherein the free layer comprises an alloy of Gd, Fe and Co.
7. The magnetic memory element of claim 1 , wherein
the electric pulse is a write pulse, and
information is recorded in the spin valve structure by applying a plurality of write pulses to control a combination of magnetization of the free layer and magnetization of the pinned layer.
8. The magnetic memory element according to claim 2 , wherein the ferrimagnetic layer and the supplemental magnetic layer are both perpendicular magnetization films.
9. The magnetic memory element according to claim 2 , wherein, one of the ferrimagnetic layer and the supplemental magnetic layer is a perpendicular magnetization film, and the other thereof is an in-plane magnetization film.
10. The magnetic memory element according to claim 2 , wherein the nonmagnetic layer includes magnesium oxide, the ferrimagnetic layer includes an alloy of Tb, Fe and Co, or an alloy of Gd, Fe and Co that are rare earth-transition metal alloys, and the supplemental magnetic layer includes an alloy of Co, Fe and B.
11. A method of driving a magnetic memory element, which has a spin valve structure having a free layer, a nonmagnetic layer, and a pinned layer, the pinned layer and the free layer sandwiching the nonmagnetic layer, and a selected one of the pinned layer and the free layer including a ferromagnetic layer made of an N-type ferrimagnetic material, a magnetic compensation point Tcomp of the N-type ferrimagnetic material being in a storage retention operation temperature region of the magnetic memory element, the method comprising:
applying a first write pulse to the spin valve structure, to cause a combination of magnetization of the free layer and magnetization of the pinned layer to be in a first combination state; and
applying a second write pulse to the spin valve structure, to cause the combination of the magnetization of the free layer and the magnetization of the pinned layer to be in a second combination state, wherein
if the pinned layer is the selected layer, the magnetizations of the pinned layer, upon applications of the first and second write pulses, have mutually different orientations, and, if the free layer is the selected layer, the magnetizations of the free layer, upon applications of the first and second write pulses, have a same orientation, and
the first and second write pulses are both electric pulse and have a same polarity.
12. The method of driving a magnetic memory element according to claim 11 , wherein the first and second write pulses pass current from the free layer to the pinned layer.
13. The method of driving a magnetic memory element according to claim 11 , wherein the first and second write pulses pass current from the pinned layer to the free layer.
14. The method of driving a magnetic memory element according to claim 12 , wherein pulse heights of the first write pulse and of the second write pulse are mutually different.
15. The method of driving a magnetic memory element according to claim 14 , wherein one of the first write pulse and the second write pulse is a pulse which changes a resistance value between the free layer and the pinned layer to a low value and has a portion of an amplitude Vp, the other pulse thereof is a pulse which changes the resistance value to a high value and has a portion of an amplitude Vap, with the amplitude Vp being smaller than the amplitude Vap.
16. The method of driving a magnetic memory element according to claim 15 , wherein the first write pulse and the second write pulse have different pulse widths, and information is recorded based on the pulse widths.
17. The method of driving a magnetic memory element according to claim 16 , wherein one of the first write pulse and the second write pulse is a pulse which changes a resistance value between the free layer and the pinned layer to a low value and has a pulse width tp, the other pulse thereof is a pulse which changes the resistance value to a high value and has a pulse width tap, with the pulse width tp being smaller than the pulse width tap.
18. The method of driving a magnetic memory element according to claim 13 , wherein pulse heights of the first write pulse and of the second write pulse are mutually different.
19. The method of driving a magnetic memory element according to claim 18 , wherein one of the first write pulse and the second write pulse is a pulse which changes a resistance value between the free layer and the pinned layer to a low value and has a portion of an amplitude Vp, the other pulse thereof is a pulse which changes the resistance value to a high value and has a portion of an amplitude Vap, with the amplitude Vp being smaller than the amplitude Vap.
20. The method of driving a magnetic memory element according to claim 19 , wherein the first write pulse and the second write pulse have different pulse widths, and information is recorded based on the pulse widths.
21. The method of driving a magnetic memory element according to claim 20 , wherein one of the first write pulse and the second write pulse is a pulse which changes a resistance value between the free layer and the pinned layer to a low value and has a pulse width tp, the other pulse thereof is a pulse which changes the resistance value to a high value and has a pulse width tap, with the pulse width tp being smaller than the pulse width tap.
22. A nonvolatile storage device, comprising:
the magnetic memory element according to claim 1 ;
a rectifying element connected in series to the magnetic memory element;
information overwrite means for generating a first write pulse to change a combination of magnetization of the free layer and magnetization of the pinned layer in a spin valve structure of the magnetic memory element into a first combination state, and a second write pulse of a same polarity as the first write pulse for changing the combination into a second combination state, and for applying the first and second write pulses to the rectifying element and the magnetic memory element to perform writing and erasing; and
read means for reading stored information by means of a quantity of current flowing in the magnetic memory element.
23. The magnetic memory element according to claim 7 , wherein the magnetic compensation temperature T comp of the N-type ferrimagnetic material is lower than a temperature reached by the ferrimagnetic layer when one of the plurality of write pulses is applied, and higher than a temperature reached by the ferrimagnetic layer when another of the plurality of write pulses is applied.