1. Beijing
National Laboratory for Condensed Matter Physics and State Key Laboratory
of Magnetism, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, P. R. China
2. NIST
Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
3. Department
of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742-2115, United States