Ginzburg-Landau theory for the conical cycloid state in multiferroics: Applications to CoCr2O4

Chuanwei Zhang,1,2 Sumanta Tewari,1,3 John Toner,4 and S. Das Sarma1 1Department of Physics, Condensed Matter Theory Center, University of Maryland, College Park, Maryland 20742, USA 2Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA 3Department of Physics and Astronomy, Clemson University, Clemson, South Carolina 29634, USA 4Department of Physics and Institute of Theoretical Science, University of Oregon, Eugene, Oregon 97403, USA Received 18 September 2008; published 30 October 2008