1. Department of Physics & Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, North Zhongshan Road 3663, 200062 Shanghai, P. R. China
2. Department
of Materials, Loughborough University, Leicestershire, LE11 3TU, England, U.K.
3. Research
Institute, Teijin Aramid, Velperweg 76, 6802
ED Arnhem, The Netherlands