The interlayer coupling field (H in ) and coercivity (H c ) were measured using micro-optical Kerr effect, and the surface roughness was obtained by using atomic force microscopy (AFM) at different points across the patterned tunnel junction. H in and H c increase with greater surface roughness. This result shows that the enhanced coercivity (H ce ) is linearly proportional to H in such as Hce=αHin. Finally, the propositional constant α has been deduced from the annealing field dependence of H in and H ce as the function of surface magnetization of pinned layer, α=(Ms–Mps)/Mps. From the results of H in and H ce in magnetic tunnel junction (MTJ) multilayer, we can infer that the surface magnetization of pinned layer is due to the interfacial morphological corrugations.