Session D40 - Poster Session I.
POSTER session, Monday afternoon, March 12
Exhibit Hall, Washington State Convention Center
White's Numerical Density Matrix Renormalization Group method is used to study 1/2 filled t-U-J Hubbard chains coupled together to form 2, 3 leg ladders in the presence of magnetic impurities. t-U-J Hamiltonian was proposed by S. Daul et al. Spin gap and spin-spin correlations are calculated for NX2, NX3 ladders with N = 16, 32 for 2 leg ladder and N = 10, 20 for 3 leg ladder. Impurity concentration of 1 magnetic atom per chain is assumed. Two impurity configurations are studied for 2 leg ladder : impurities on a single rung at the center of the ladder, impurities on different rungs. For 3 leg ladder impurity configurations are : impurities on two collinear rungs in the center of the ladder, two impurities on a rung and the third on a non collinear rung, impurities on non collinear rungs.