1. Department of Physics, Temple University, Philadelphia, Pennsylvania, USA
2. Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California, USA
3. Peter-Grünberg-Institut PGI-6, Forschungszentrum Jülich GmbH, Jülich, Germany
4. Department of Physics, University of California Davis, Davis, California, USA
5. Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA