1998/12/31 by Chitoshi Yasuda, Akihide Oguchi · 2 citations
Materials Science · Physics and Astronomy · #Advanced Condensed Matter Physics #Antiferromagnetism #Coherent potential approximation #Ground state #Heisenberg model #Impurity #Iron-based superconductors research #Percolation (cognitive psychology) #Percolation threshold #Physics of Superconductivity and Magnetism #Spin (aerodynamics) #cond-mat.dis-nn #cond-mat.mtrl-sci
paper · pdf · doi:10.1143/jpsj.68.2773
6 pages, 1 figures
arxiv created 1999/06/07 · openalex publication_date 1999/08/15 · arxiv updated 2009/11/30 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The spin-wave theory and the coherent potential approximation are applied to a spin S Heisenberg antiferromagnet with nonmagnetic impurities on square lattice. The impurity effects are taken into account by substituting S(1-x) for S and using the coherent potential approximation to the exchange interaction, where x is the impurity concentration. At T=0 for S=1/2 the critical impurity concentration xc of the Neel state is 0.303 and the percolation threshold xp is 0.500. The ground state in xc<x<xp is the disordered state with the spin gap. For S>=1 the long range Neel order vanishes at xp=0.500. These results explain qualitatively the experimental results of La2Cu(1-x)Mg(x)O4 (S=1/2) and K2Mn(1-x)Mg(x)F4 (S=5/2). The difference of xc between these materials is caused by the decrease in the magnitude of the effective spin with impurity doping. The spin gap is expected to be observed for La2Cu(1-x)Mg(x)O4 in xc<x<xp at low temperatures.