Magnetoresistance effect element

1. A magnetoresistance effect element, comprising:

a first ferromagnetic layer;

a second ferromagnetic layer; and

a tunnel barrier layer that is interposed between the first ferromagnetic layer and the second ferromagnetic layer,

wherein the tunnel barrier layer is a stacked body including one or more first oxide layers and one or more second oxide layers having a composition which is different from a composition of the one or more first oxide layers,

a first oxide layer of the one or more first oxide layers includes an oxide containing a metal or an alloy which is expressed by General Formula (I),

A 1-x B x   (I),

a second oxide layer of the one or more second oxide layers includes an oxide containing a metal or an alloy which is expressed by General Formula (II),

A 1-y B y   (II), wherein

in each of General Formula (I) and General Formula (II),

A is independently Mg or Zn,

B is independently at least one type of metal selected from the group consisting of Al, Ga, and In, and

x satisfies 0<x<0.5 and y satisfies 0.5<y≤1, and |y−x|≥0.005, and

wherein

at least one of the first oxide layer or the second oxide layer has a spinel structure, and

the tunnel barrier layer is a stacked body which includes two first oxide layers and in which the second oxide layer is interposed between the two first oxide layers.

2. The magnetoresistance effect element according to claim 1 , wherein the first ferromagnetic layer is formed on a substrate, the first oxide layer is stacked on a surface of the first ferromagnetic layer opposite to the substrate, and the second oxide layer is stacked on a surface of the first oxide layer opposite to the first ferromagnetic layer.

3. The magnetoresistance effect element according to claim 1 , wherein a thickness of the first oxide layer is thinner than a thickness of the second oxide layer.

4. The magnetoresistance effect element according to claim 1 , wherein a thickness of the tunnel barrier layer is equal to or less than 3 nm.

5. The magnetoresistance effect element according to claim 1 , wherein the first oxide layer and the second oxide layer have a disordered spinel structure.

6. A method of manufacturing the magnetoresistance effect element according to claim 1 including: the first ferromagnetic layer; the second ferromagnetic layer; and the tunnel barrier layer that is interposed between the first ferromagnetic layer and the second ferromagnetic layer, the tunnel barrier layer being the stacked body including the one or more first oxide layers and the one or more second oxide layers with the composition which is different from the composition of the first oxide layer, the method comprising:

performing a heat treatment after stacking each of the first and second oxide layers.

7. A magnetoresistance effect element, comprising:

a first ferromagnetic layer;

a second ferromagnetic layer; and

a tunnel barrier layer that is interposed between the first ferromagnetic layer and the second ferromagnetic layer,

wherein the tunnel barrier layer is a stacked body including one or more first oxide layers and one or more second oxide layers having a composition which is different from a composition of the one or more first oxide layers,

a first oxide layer of the one or more first oxide layers includes an oxide containing a metal or an alloy which is expressed by General Formula (I),

A 1-x B x   (I),

a second oxide layer of the one or more second oxide layers includes an oxide containing a metal or an alloy which is expressed by General Formula (II),

A 1-y B y   (II), wherein

in each of General Formula (I) and General Formula (II),

A is independently Mg or Zn,

B is independently at least one type of metal selected from the group consisting of Al, Ga, and In, and

x satisfies 0<x<0.5 and y satisfies 0.5<y≤1, and |y−x|≥0.005, and

wherein

at least one of the first oxide layer or the second oxide layer has a spinel structure, and

a thickness of the first oxide layer is thinner than a thickness of the second oxide layer.

8. The magnetoresistance effect element according to claim 7 , wherein the first ferromagnetic layer is formed on a substrate, the first oxide layer is stacked on a surface of the first ferromagnetic layer opposite to the substrate, and the second oxide layer is stacked on a surface of the first oxide layer opposite to the first ferromagnetic layer.

9. The magnetoresistance effect element according to claim 7 , wherein the tunnel barrier layer is a stacked body which includes two first oxide layers and in which the second oxide layer is interposed between the two first oxide layers.

10. The magnetoresistance effect element according to claim 7 , wherein a thickness of the tunnel barrier layer is equal to or less than 3 nm.

11. The magnetoresistance effect element according to claim 7 , wherein the first oxide layer and the second oxide layer have a disordered spinel structure.