Suppressed magnetization in   La$_{0.7}$Ca$_{0.3}$MnO$_3$/YBa$_2$Cu$_3$O$_{7-\delta}$ superlattices
  We studied the magnetic properties of La$_{0.7}$Ca$_{0.3}$MnO$_3$ / YBa$_2$Cu$_3$O$_{7-\delta}$ superlattices. Magnetometry showed that with increasing YBa$_2$Cu$_3$O$_{7-\delta}$ layer thickness the saturation magnetization per La$_{0.7}$Ca$_{0.3}$MnO$_3$ layer decreases. From polarized neutron reflectometry we determined that this magnetization reduction is due to an inhomogenous magnetization depth profile arising from the suppression of magnetization near the La$_{0.7}$Ca$_{0.3}$MnO$_3$ / YBa$_2$Cu$_3$O$_{7-\delta}$ interface. Electron energy loss spectroscopy indicates an increased 3d band occupation of the Mn atoms in the La$_{0.7}$Ca$_{0.3}$MnO$_3$ layers at the interface. Thus, the suppression of ferromagnetic order at the La$_{0.7}$Ca$_{0.3}$MnO$_3$ / YBa$_2$Cu$_3$O$_{7-\delta}$ interface is most likely due to charge transfer between the two materials. 
A. Hoffmann, S. G. E. te Velthuis, Z. Sefroui, J. Santamaria, M. R.   Fitzsimmons, S. Park, and M. Varela