Doping dependence of the tetragonal-orthorhombic phase transition in the superconducting compound La2-xSrxCuO4±δ

The phase transition from tetragonal to orthorhombic structure in the high-temperature superconductor La2-xSrxCuO4+/-delta (La214) has been studied by means of elastic neutron scattering. Both underdoped (x = 0.09) and over-doped (x = 0.17) compounds have been investigated. From the temperature dependence of the superstructure peaks, we are able to estimate the critical exponent beta, which is found to increase with increasing x. We also observe that the temperature interval over which the critical behaviour appears to be valid is unusually large and strongly doping-dependent.