1. Institute for Solid State Physics and Optics Wigner Research Centre for Physics P.O. Box 49 Budapest H‐1525 Hungary
2. Eötvös Loránd University P.O. Box 32 Budapest H‐1518 Hungary
3. Department of Physics Kent State University Kent OH 44242 USA
4. Materials Sciences Graduate Program and Advanced Materials and Liquid Crystal Institute Kent State University Kent OH 44242 USA