Neutron scattering study of the effects of dopant disorder on the superconductivity and magnetic order in stage-4 La_2CuO_{4+y}

TL;DR

This study uses neutron scattering to investigate how dopant disorder affects superconductivity and magnetic order in stage-4 La_2CuO_{4+y}, revealing that disorder reduces T_c and enhances magnetic order.

Contribution

It demonstrates that controlling dopant disorder via cooling rate influences superconducting and magnetic properties in La_2CuO_{4+y}.

Findings

Disordered oxygen dopants form a 3D superlattice.

Quenched disorder reduces T_c by ~5 K.

Disorder enhances spin density wave order.

Abstract

We report neutron scattering measurements of the structure and magnetism of stage-4 La_2CuO_{4+y} with T_c ~42 K. Our diffraction results on a single crystal sample demonstrate that the excess oxygen dopants form a three-dimensional ordered superlattice within the interstitial regions of the crystal. The oxygen superlattice becomes disordered above T ~ 330 K, and a fast rate of cooling can freeze-in the disordered-oxygen state. Hence, by controlling the cooling rate, the degree of dopant disorder in our La_2CuO_{4+y} crystal can be varied. We find that a higher degree of quenched disorder reduces T_c by ~ 5 K relative to the ordered-oxygen state. At the same time, the quenched disorder enhances the spin density wave order in a manner analogous to the effects of an applied magnetic field.