Interface stability in CoFe and CoFeB based multilayers

We report grazing incidence x-ray scattering measurements made during in situ annealing of multilayers based on CoFe and CoFeB. The layer and interface structure of Co(80)Fe(20)/Ru multilayers grown on Si/Al(2)O(3) were found to be stable at all temperatures up to 400 degrees C. In contrast, Co(64)Fe(16)B(20)/Ru multilayers, also grown on Si/Al(2)O(3), showed loss of Kiessig fringe visibility above 270 degrees C but no evidence of Co(64)Fe(16)B(20)/Ru interface roughening on recrystallization of the Co(64)Fe(16)B(20). We associate the changes in Messig fringe amplitude with increase in interface width, partly due to increase in the topological roughness, measured from the diffuse scattering away from the Bragg peaks, at the bottom Co(64)Fe(16)B(20)/Al(2)O(3) interface.