Momentum transfer resolved memory in a magnetic system with perpendicular anisotropy

We have used resonant, coherent soft x-ray scattering to measure wave vector resolved magnetic domain memory in Co/Pd multilayers. The technique uses angular cross correlation functions and can be applied to any system with circular annuli of constant values of scattering wave vector {\bf q}. In our Co/Pd film, the memory exhibits a maximum at {\bf q}=0.0384 nm$^{\rm -1}$ near initial reversal that decreases in magnitude as the magnetization is further reversed. The peak is attributed to bubble domains that nucleate reproducibly near initial reversal and which grow into a labyrinth domain structure that is not reproduced from one magnetization cycle to the next.