Impurity Induced Antiferromagnetism in Spin-1/2 Heisenberg Two-Leg Ladder Systems

Abstract

Based on the phase Hamiltonian representation of a spin-1/2 Heisenberg two-leg ladder system coupled antiferromagnetically, which has a spin gap if clean, it is shown that a non-magnetic impurity replacing a spin induces a staggered spin modulation. This results in the long range order of antiferromagnetism in the presence of three-dimensional coupling between the ladders. This will be in accordance with a recent experimental observation by Azuma et al. on Sr(Cu 1- x Zn x ) 2 O 3 .