Annealing Effects on the Microstructure and Magnetoresistance of Magnetic Tunnel Junctions with MgO-Barrier

摘要

Thermal annealing effect on the microstructure and potential distribution for Co_(40)Fe_(40)B_(20)/MgO/ Co_(40)Fe_(40)B_(20) magnetic tunnel junctions is investigated by high-resolution electron microscopy and electron holography. The experimental results demonstrate that thermal annealing could result in notable crystallization in both ferromagnetic electrodes and MgO barriers and could also yield sharper interfaces and symmetrical potential for CoFeB/MgO/CoFeB junctions. The effective barrier height for CoFeB/MgO is estimated to be about 2.45 eV, in fundamentally agreement with the data of the magnetoresistance and the I-V characteristics. These results suggest that the microstructure of the MTJs play an important role for the coherent tunneling processes that give rise to the large tunnel magnetoresistance.