1. Department of Materials Science and Engineering, Superconducting Materials Laboratory; Shibaura Institute of Technology; 3-7-5 Toyosu, Koto-ku Tokyo 135-8548 Japan
2. Institute of Experimental Physics; Saarland University; P.O. Box 151150 66041 Saarbrücken Germany
3. Institute of Experimental Physics, Material Physics Laboratory; Slovak Academy of Sciences; Watsonova 47 04001 Kosice Slovak