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 having a spinel structure and one or more second oxide layers having a spinel structure with a composition which is different from a composition of the first oxide layer.

2. The magnetoresistance effect element according to claim 1 , wherein

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

A 1-x B x   (I)

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

A 1-y B y   (II), and wherein,

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

A's are independently Mg or Zn,

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

x and y satisfy 0<x≤1, 0<y≤1, and |y−x|≥0.005.

3. The magnetoresistance effect element according to claim 2 , wherein x satisfies 0<x<0.5 and y satisfies 0.5<y≤1, or x satisfies 0.5<x≤1 and y satisfies 0<y<0.5.

4. The magnetoresistance effect element according to claim 3 , wherein x satisfies 0<x<0.5 and y satisfies 0.5<y≤1.

5. The magnetoresistance effect element according to claim 4 , 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.

6. The magnetoresistance effect element according to claim 4 , 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.

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

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