Neutron scattering study onLa1.9Ca1.1Cu2O6+δandLa1.85Sr0.15CaCu2O6+δJournal Articles
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abstract
We present neutron scattering data on two single crystals of the high
temperature superconductor La2-x(Ca,Sr)xCaCu2O6+delta. The Ca0.1-doped crystal
exhibits a long-range antiferromagnetically ordered ground state. In contrast,
the Sr0.15-doped crystal exhibits short-range antiferromagnetic order as well
as weak superconductivity. In both crystals antiferromagnetic correlations are
commensurate; however, some results on the Ca0.1-doped crystal resemble those
on the spin-glass phase of La2-xSrxCuO4, 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 inter-bilayer 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 CuO2
planes in more detail. For comparison we show X-ray diffraction and
magnetization data. In particular, for the Ca0.1-doped crystal these
measurements reveal valuable information on the spin-glass transition as well
as a second anomaly associated with the Neel transition.
