UNIAXIAL PRESSURE-DEPENDENCE OF T(C) FROM HIGH-RESOLUTION DILATOMETRYOF UNTWINNED LA2-XSRXCUO4 SINGLE-CRYSTALS

We have carried out high-resolution dilatometry experiments on a serie s of high-quality single crystals of La2-xSrCuO4 with various Sr conte nt on both the under- and overdoped side of the T(c)(x) phase diagram. A simple in situ technique was applied to prevent the usual twinning of the samples in the low-temperature orthorhombic (LTO) phase, which allows us to study the full anisotropy of the thermal expansion of the LTO phase. From the anomalies in the linear expansivities DELTAalpha( i) (i=a,b,c) at T(c) we deduce all three uniaxial stress (dT(c)/dp(i)) and strain (dT(c)/depsilon(i)) dependences, which turn out to be larg e and almost cancel for hydrostatic pressure.