Structural effects of hydrostatic pressure in Sr1-xMxCuO2 (M=La,Ca) and Sr4Cu6O10.

Abstract

Pressure effects on the tetragonal infinite-layer structure were studied in superconducting ${\mathrm{Sr}}_{0.9}$${\mathrm{La}}_{0.1}$${\mathrm{CuO}}_{2}$ (electron-doped) and ${\mathrm{Sr}}_{0.7}$${\mathrm{Ca}}_{0.3}$${\mathrm{CuO}}_{2}$ (hole-doped) samples, and in an insulating nonsuperconducting ${\mathrm{Sr}}_{0.14}$${\mathrm{Ca}}_{0.86}$${\mathrm{CuO}}_{2}$ sample, using time-of-flight neutron powder diffraction. Neutron-diffraction measurements, with the sample at room temperature, were performed at several hydrostatic pressures up to \ensuremath{\approxeq}0.6 GPa on each of the three samples, using a helium-gas pressure cell. The measured compressibilities, which are similar for the three samples, show a large anisotropy, and are in a good agreement with first-principles calculations performed for undoped ${\mathrm{Sr}}_{0.7}$${\mathrm{Ca}}_{0.3}$${\mathrm{CuO}}_{2}$. Atomic size effects of the A atom in A${\mathrm{CuO}}_{2}$ on the crystal lattice are discussed and are compared with the pressure effects. A relation is found between the in-plane compressibilities among n-layer (n=1,2,3 . . .,\ensuremath{\infty}) structures of high-${\mathit{T}}_{\mathit{c}}$ superconductors.