Magnetoresistance effect element

A magnetoresistance effect element comprising:

• a first ferromagnetic metal layer;
• a second ferromagnetic metal layer;
• and
• a tunnel barrier layer that is sandwiched between the first and second ferromagnetic metal layers,
• wherein the tunnel barrier layer has a spinel structure represented by a composition formula AGa2Ox (0<x≤4), and
• an A-site is a non-magnetic divalent cation which is one or more selected from a group consisting of magnesium, zinc and cadmium, and wherein
• the tunnel barrier layer comprises:
• at least one lattice-matched portion that is lattice-matched with both of the first ferromagnetic metal layer and the second ferromagnetic metal layer;
• and at least one lattice-mismatched portion that is not lattice-matched with at least one of the first ferromagnetic metal layer and the second ferromagnetic metal layer, and
• when viewed as an inverse Fourier transform image in a stacking direction of a cross-sectional crystal lattice image of the interface between the tunnel barrier layer and the first and/or the second ferromagnetic metal layer, a lattice-matched portion is made up of a plurality of sequential, continuously-connected lattice lines, and a lattice-mismatched portion is made up of a plurality of sequential, non-continuously-connected lattice lines and/or no lattice lines.