Synthesis, crystal structure and magnetic properties of the spin ladder compounds La2(Cu1-xZnx)2O5 and La8(Cu1-xZnx)7O19

The influence of Zn-doping on the crystal structure and magnetic properties of the spin ladder compounds La2Cu2O5 (4-leg) and La8Cu7O19 (5-leg) have been investigated. The La2(Cu1-xZnx)2O5 and La8(Cu1-xZnx)7O19 solid solutions were obtained as single phases with x=0-0.1 via the solid-state reaction method in the temperature range between 1005-1010 deg. C and 1015-1030 deg. C in oxygen and air atmospheres, respectively. The lattice parameters a and c of the monoclinic crystal structures as well as the unit cell volume V increase with increasing x, while b and β decrease for both series. The magnetic susceptibilities χ of both series show a very similar behavior on temperature as well as on Zn-doping, which is supposed to be due to the similar Cu-O coordination in both La2Cu2O5 and La8Cu7O19. For low Zn-doping (x=<0.04), a spin-chain like behavior is found. This quasi-one-dimensional behavior is strongly suppressed in both series for x>=0.04. Here, the maximum (characteristic for spin chains) in χ(T) disappears and χ(T) decreases monotonically with increasing temperature