Magnetic memory including a magnetoresistive element
View Patent ↗A magnetic memory includes a magnetoresistive element. The magnetoresistive element includes a reference layer having an invariable magnetization direction, a storage layer having a variable magnetization direction, and a spacer layer provided between the reference layer and the storage layer. The storage layer has a multilayered structure including first and second magnetic layers, the second magnetic layer is provided between the first magnetic layer and the spacer layer and has a magnetic anisotropy energy lower than that of the first magnetic layer, and an exchange coupling constant Jex between the first magnetic layer and the second magnetic layer is not more than 5 erg/cm 2 .
1. A magnetic memory comprising a magnetoresistive element,
the magnetoresistive element comprising:
a reference layer having an invariable magnetization direction;
a storage layer having a variable magnetization direction; and
a spacer layer provided between the reference layer and the storage layer, and
wherein the storage layer has a multilayered structure including a first magnetic layer and a second magnetic layer,
the second magnetic layer is provided between the first magnetic layer and the spacer layer and has a magnetic anisotropy energy lower than that of the first magnetic layer,
an exchange coupling constant Jex between the first magnetic layer and the second magnetic layer is not more than 5 erg/cm 2 , and
a metal layer is provided between the first magnetic layer and the second magnetic layer, and contains at least one element selected from the group consisting of Fe, Ni, and Co.
2. A magnetic memory comprising a magnetoresistive element,
the magnetoresistive element comprising:
a reference layer having an invariable magnetization direction;
a storage layer having a variable magnetization direction; and
a spacer layer provided between the reference layer and the storage layer, and
wherein the storage layer has a multilayered structure including a first magnetic layer and a second magnetic layer,
the second magnetic layer is provided between the first magnetic layer and the spacer layer and has a magnetic anisotropy energy lower than that of the first magnetic layer,
an exchange coupling constant Jex between the first magnetic layer and the second magnetic layer is not more than 5 erg/cm 2 , and
the storage layer further comprises a third magnetic layer provided on a side opposite to the second magnetic layer with respect to the first magnetic layer and has a magnetic anisotropy energy lower than that of the first magnetic layer.
3. The magnetic memory according to claim 2 , wherein an exchange coupling constant Jex between the first magnetic layer and the third magnetic layer is not less than 5 erg/cm 2 .
4. A magnetic memory comprising a magnetoresistive element,
the magnetoresistive element comprising:
a reference layer having an invariable magnetization direction;
a storage layer having a variable magnetization direction; and
a spacer layer provided between the reference layer and the storage layer, and
wherein the storage layer has a multilayered structure including a first magnetic layer and a second magnetic layer,
the second magnetic layer is provided between the first magnetic layer and the spacer layer and has a magnetic anisotropy energy lower than that of the first magnetic layer,
an exchange coupling constant Jex between the first magnetic layer and the second magnetic layer is not more than 5 erg/cm 2 , and
the storage layer further comprises a fourth magnetic layer provided on a side opposite to the second magnetic layer with respect to the first magnetic layer and has a magnetic anisotropy energy higher than that of the first magnetic layer.
5. The magnetic memory according to claim 4 , wherein at least one magnetic metal element selected from the group consisting of Co, Fe, Ni, and Mn or at least one nonmagnetic element selected from the group consisting of Ti, V, Cr, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Hf, Ta, W, Re, Os, Ir, Pt, and Au is added to the first magnetic layer.
6. The magnetic memory according to claim 4 , wherein the first magnetic layer and the fourth magnetic layer are essentially made of a compound or an alloy containing at least one magnetic metal element selected from the group consisting of Co, Fe, Ni, and Mn and at least one nonmagnetic element selected from the group consisting of Ti, V, Cr, Cu, Zn, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Hf, Ta, W, Re, Os, Ir, Pt, and Au, and a composition ratio of the magnetic metal element and the nonmagnetic element changes between the first magnetic layer and the fourth magnetic layer.
7. The magnetic memory according to claim 1 , wherein letting K U1 be a magnetic anisotropy energy density of the first magnetic layer, t 1 be a thickness of the first magnetic layer, K U2 be a magnetic anisotropy energy density of the second magnetic layer, t 2 be a thickness of the second magnetic layer, A be an average exchange stiffness constant of the first magnetic layer and the second magnetic layer, M s av be an average saturation magnetization of the first magnetic layer and the second magnetic layer, D s be a diameter of the magnetoresistive element which ensures the same energy barrier in a process of causing reversal through two magnetic domains and a process of causing reversal along an axis of hard magnetization in a single magnetic domain in a magnetization reversal process, and Na be a demagnetizing factor in a film thickness direction of the multilayered structure including the first magnetic layer and the second magnetic layer, the diameter D s is given by
D
s
=
6
A
(
K
u
1
t
1
+
K
u
2
t
2
)
(
K
u
1
t
1
+
K
u
2
t
2
)
-
2
π
(
M
s
av
)
2
(
N
a
-
1
2
)
(
t
1
+
t
2
)
and a diameter D of the storage layer satisfies
D<1.5 D s .