Structural and magnetic properties of Co/alpha-Al2O3/Fe magnetic tunneling junction system: Ab initio investigations

Abstract

Using the density functional theory calculations, the structural effects on the spin polarizations and change of tunneling magnetoresistance for Co/alpha-Al2O3/Fe magnetic tunneling junction were predicted. Hybridization of 3d orbitals of ferromagnetic atoms and O 2p orbital resulted in the covalent bond formations of Co-O and Fe-O at the interface and, subsequently, layer fluctuations of interfacial slabs occurred to the extent of 34.5% and 37.2% of the interlayer distances, 1.94 angstrom for Co and 1.91 angstrom for Fe. The magnetic moment of Co-interface atoms was enhanced to 2.03 mu(B), while that for the Fe-interface atoms was reduced to 1.59 mu(B) from the corresponding bulk magnetization. Large asymmetric distributions of layer decomposed density of states for majority and minority spin electrons led the spin polarizations of 35.2% and 65.9% for top and bottom ferromagnetic electrodes, respectively. The change of magnetoresistance was calculated to be 37.7%.