Exchange anisotropy , disorder , and frustration in diluted , predominantly ferromagnetic , Heisenberg spin systems

Chenggang Zhou, Malcolm P. Kennett, Xin Wan,* Mona Berciu, and R. N. Bhatt Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544, USA TCM Group, Cavendish Laboratories, Cambridge University, Madingley Road, Cambridge CB3 0HE, United Kingdom National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310, USA Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada BC V6T 1Z1 ~Received 14 October 2003; revised manuscript received 10 February 2004; published 19 April 2004!