This work was supported by the Samsung Advanced Institute of Technology. The STEM work carried out at the Center for Functional Nanomaterials, Brookhaven National Laboratory (BNL), was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886. The neutron scattering activities by Y.S.L. were supported by DOE under Grant No. DE-FG02-07ER46134. Use of the National Synchrotron Light Source, BNL, was supported by the DOE, Office of Science, Office of Basic Energy Sciences, and by DOE-EERE under the Batteries for Advanced Transportation Technologies (BATT) Program, under Contract No. DE-AC02-98CH10886. The identification of commercial product or trade name does not imply recommendation by the National Institute of Standards and Technology. This work made use of the Shared Experimental Facilities supported in part by the MRSEC Program of the National Science Foundation under award number DMR-0819762. This work was also supported by a user project of ORNL’s Center for Nanophase Materials Sciences (CNMS), which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. We appreciate the assistance with magnetic SQUID measurements from S. Chu at MIT.