1. State Key Laboratory of Rare Earth Resource UtilizationChangchun Institute of Applied ChemistryChinese Academy of Sciences Changchun 130022 P. R. China
2. University of Science and Technology of China Hefei 230026 P. R. China
3. State Key Laboratory for Magnetic Resonance and Atomic and Molecular PhysicsWuhan Institute of Physics and MathematicsChinese Academy of Sciences Wuhan 430071 China