Nonmagnetic impurity effect of the S = 1/2 spin ladder system (pipdH)2Cu1−xZnxBr4

We report the synthesis and the magnetic susceptibility of (pipdH)2Cu1−xZnxBr4 (pipd=piperidinium), which is a nonmagnetic impurity-doped S = 1/2 spin ladder system. The samples were synthesized from a solution by using a slow evaporation method. Samples were confirmed to be in a single phase and to have the same crystal structure as the pure system (pipdH)2CuBr4 by using X-ray diffraction measurements. To check the magnetic properties, we performed magnetic susceptibility and magnetization measurements with a superconducting quantum interference device magnetometer. A plot of the inverse magnetic susceptibility indicates the presence of dominant antiferromagnetic coupling. The magnetic susceptibility shows a broad maximum due to low dimensionality and a spin gap behavior related to the two-leg spin ladder at low temperature. The spin gap Δ and the Curie constants of Zn-doped samples, as estimated from an analysis of the magnetic susceptibility, monotonically decrease as the Zn concentration decreases. A nonmagnetic impurity of S = 1/2 spin ladder system affects the spin gap.