Study of ultrathin CoFeB films on MgO (001) using polarized neutron reflectivity

In the present work, CoFeB film on MgO has been studied using Polarized Neutron Reflectivity. For this purpose, three samples were prepared on MgO (001) substrates with varying thickness of CoFeB layers. Structural information as 88 obtained from XRR and SIMS measurements was used to analyze the PNR data. The average magnetic moment of CoFeB layer comes out to be around 1.8 μB/formula unit with no signature of magnetic dead layer at CoFeB/ MgO interface. Best fit of the data was obtained with two interfacial layers conjectured at the two interfaces with MgO and Au with 30 % reduced and zero magnetic moment respectively. The higher reduction in magnetic moment of the interfacial layer can partly be attributed to a higher Boron concentration in the interfacial region with MgO as observed from SIMS measurements. (author)