Neutron scattering study on La{sub 1.9}Ca{sub 1.1}Cu{sub 2}O{sub 6+{delta}} and La{sub 1.85}Sr{sub 0.15}CaCu{sub 2}O{sub 6+{delta}}

We present neutron scattering data on two single crystals of the high temperature superconductor La{sub 2-x}(Ca,Sr){sub x}CaCu{sub 2}O{sub 6+{delta}}. The Ca{sub 0.1}-doped crystal exhibits a long-range antiferromagnetically ordered ground state. In contrast, the Sr{sub 0.15}-doped crystal exhibits short-range antiferromagnetic order as well as weak superconductivity. In both crystals antiferromagnetic correlations are commensurate; however, some results on the Ca{sub 0.1}-doped crystal resemble those on the spin-glass phase of La{sub 2-x}Sr{sub x}CuO{sub 4}, where magnetic correlations became incommensurate. In addition, both crystals show a structural transition from tetragonal to orthorhombic symmetry. Quite remarkably, the temperature dependence and correlation length of the magnetic order is very similar to that of the orthorhombic distortion. We attribute this behavior to an orthorhombic strain-induced interbilayer magnetic coupling, which triggers the antiferromagnetic order. The large size of the crystals made it also possible to study the magnetic diffuse scattering along rods perpendicular to the CuO{sub 2} planes in more detail. For comparison we show x-ray diffraction and magnetization data. In particular, for the Ca{sub 0.1}-doped crystal these measurements reveal valuable information on the spin-glass transition as well as a second anomaly associated with the Neel transition.