Microstructure and magnetoresistance of MgO thin film with CoFeB and CoFeC underlayers

Abstract The MgO thin films were deposited on CoFeB and CoFeC magnetic underlayers at room temperature by magnetron sputtering. The microstructures of the MgO films were investigated by high-resolution transmission electron microscopy (TEM). The results showed that the atomically resolved MgO (0 0 1) lattice planes were parallel to the film plane for MgO layers with CoFeB and CoFeC underlayers. Besides, the X-ray diffraction analyses indicated that the intensity of MgO (0 0 2) diffraction peak was enhanced as the MgO layer was deposited on the CoFeC underlayer. The relatively large tunnelling magnetoresistance ratio for the as-deposited film was obtained at room temperature as the MgO layer was deposited on the CoFeC underlayer. The larger tunnelling magnetoresistance ratio in as-deposited CoFeC/MgO/CoFe magnetic tunnel junction may be related to the higher (0 0 1) texture of the MgO barrier.