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,
• the tunnel barrier layer comprises a lattice-matched portion and a lattice-mismatched portion, the lattice-matched portion lattice-matching with both of the first and second ferromagnetic metal layers, the lattice-mismatched portion not lattice-machining with at least one of the first and second ferromagnetic metal layers,
• an underlayer is provided underneath the first ferromagnetic metal layer on a side opposite to the tunnel barrier layer,
• the underlayer has a NaCl crystal structure oriented in a (001) orientation, and the underlayer is made of a nitride containing at least one element selected from a group consisting of Ti, Zr, Nb, V, Hf, Ta, Mo, W, B, Al and Ce, and wherein
• when viewed as an inverse Fourier transform image in a stacking direction of a cross-section TEM 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, and
• wherein the tunnel barrier layer is expressed by a chemical formula of AB2OX (0<X≤4), and has a spinel structure in which cations are arranged in a disordered manner,
• A represents a divalent cation that is either Mg or Zn, and
• B represents a trivalent cation that includes a plurality of elements selected from a group consisting of Al, Ga, and In.