Effect of interface on magnetic properties of Co20Fe60B20 in ion-beam sputtered Si/CoFeB/MgO and Si/MgO/CoFeB bilayers

Effect of interface on magnetic properties of Co20Fe60B20 in ion-beam sputtered Si/MgO/CoFeB(top) and Si/CoFeB(bottom)/MgO bilayers is reported. The X-ray reflectivity and magneto-optical Kerr effect analysis revealed that, the interface between bottom MgO and top CoFeB is sensitive to the MgO growth process (post-oxidation, ion-assisted and reactive growth) and its process parameters (assist-ion energy). An increase in interface width from 0.17 nm to 0.47 nm correlates to increase in coercivity from 6 Oe to 34 Oe, decrease of in-plane uniaxial magnetic anisotropy (UMA) from 8×103 to 5×103 J/m3 and changes in magnetization reversal. In contrast, the CoFeB(bottom)/MgO interface shows different magnetic behavior and no UMA. - Highlights: ► Dependence of the magnetic response of CoFeB on interface with MgO. ► Growth methods studied for MgO are post-oxidation, reactive and ion-assisted growth. ► Significant amount of in-plane magnetic anisotropy observed for CoFeB(top)/MgO. ► Absence of in-plane magnetic anisotropy in MgO/CoFeB(bottom)