First-principles calculations on magnetic properties of interface-rippled Co∕α-Al2O3∕Co

The effects of the interface fluctuations on the magnetic properties of a Co∕α-Al2O3∕Co magnetic tunnel junction were intensively investigated using first-principles calculations. Hybridization of Co-3d and O-2p orbitals resulted in the covalent bonds between Co and three O atoms at the interface of Co(111)∕α-Al2O3(0001) and, subsequently, interfacial Co atoms became undulated as much as 34.6% of the interlayer distance measured in the z direction. The magnetic moment of Co atoms at the rippled interface was enhanced to 1.95μB, while the value of the other ferromagnetic Co atoms remained unchanged. Significantly induced minority-spin density of states at the Fermi energy of the Co-interface atoms led to a highly negative spin polarization, −52.0%, at the junction interface. Interestingly, the spin polarization value for the barrier layer was in the range of −6.3%–59.2%.