[1] MIT, DEPT ELECT ENGN, CAMBRIDGE, MA 02139 USA
[2] CNRS, GRP TRANSITIONS PHASE, GRENOBLE, FRANCE
[3] MIT, DEPT PHYS, CAMBRIDGE, MA 02139 USA
[4] PENN STATE UNIV, MAT RES LAB, UNIVERSITY PK, PA 16802 USA
[5] PENN STATE UNIV, SOLID STATE PROGRAM, UNIVERSITY PK, PA 16802 USA