Evolution of Spin Stripe Order in Cuprate Superconductor Nd-LSCO under Applied Hydrostatic Pressure

Copper based superconductors have been of interest since 1986 due to their high superconducting temperatures and rich phase diagrams. Nd_0.4La_1.6-xSr_xCuO₄ (Nd-LSCO) is particularly interesting because of co-existence between strong charge and spin stripe phases and superconductivity, along with a sharp increase in magnetic scattering intensity at low temperatures due to magnetic coupling between Cu and Nd moments. Both charge and spin stripe phases are hypothesized to compete with superconductivity. The goal of this study is to explore how the magnetic correlations in this compound evolve under applied hydrostatic pressure (a tuning mechanism which is known to dramatically enhance superconductivity).

We have performed neutron diffraction measurements on high quality single crystal samples of Nd-LSCO (x=0.125) using the VERITAS and SNAP beamlines at Oak Ridge National Laboratory. An AlCuBe clamp cell was used to pressurize these samples up to 1.7GPa. Results show an increase in the magnetic correlation length, persisting up to room temperature at maximum pressure. Applied pressure is also observed to suppress the high temperature tetragonal-to-orthorhombic transition (from ~450K to ~300K at 1.7 GPa), while slightly increasing the low temperature orthorhombic-to-tetragonal transition (from ~68K to ~80K) under the same conditions.