Electronic structures of new tunnel barrier spinel MgAl ₂ O ₄ : first‐principles calculations

Abstract

Abstract The electronic structures of spinel MgAl 2 O 4 and MgO tunnel barrier materials were investigated using first‐principles density functional theory calculations. Our results show that similar electronic structures are found for the MgAl 2 O 4 and MgO tunneling barriers. The calculated direct energy gaps at the Γ‐point are about 5.10 eV for MgAl 2 O 4 and 4.81 eV for MgO, respectively. Because of the similar feature in band structures from Γ high‐symmetry point to F point (Δ band), the coherent tunneling effect might be expected to appear in MgAl 2 O 4 ‐based MTJs like in MgO‐based MTJs. The small difference of the surface free energies of Fe (2.9 J·m −2 ) and MgAl 2 O 4 (2.27 J·m −2 ) on the {100} orientation, and the smaller lattice mismatch between MgAl 2 O 4 and ferromagnetic electrodes than that between MgO and ferromagnetic electrodes, the spinel MgAl 2 O 4 can substitute MgO to fabricate the coherent tunneling and chemically stable magnetic tunnel junction structures, which will be applied in the next generation read heads or spintronic devices.