Speaker
Description
Recently, the discovery of superconductivity in the Sr-doped nickelates RNiO$_2$ (R = Pr, Nd) has attracted widespread attention. The synthesis of the RNiO2 compounds has been achieved by topotactic reduction of the non-superconducting perovskite phase RNiO$_3$, removing oxygen from the crystal lattice in a controlled fashion. Remarkably, new electronic and magnetic phases can also occur in oxygen vacant phases RNiO$_{3-x}$ with intermediate oxygen content 0 < x < 1. For instance, while LaNiO$_3$ remains paramagnetic down to lowest temperatures, long-range antiferromagnetic order emerges in LaNiO$_{2.5}$. However, it has not been clarified yet whether the new electronic and magnetic phases are accompanied by structural phase transitions. Hence, we aim to use the highly sensitive Neutron Larmor diffraction (LD) technique to investigate structural changes that possibly coincide with the electronic and magnetic transitions emerging in oxygen-deficient phases of RNiO$_{3-x}$. As a first step, we report here that LD is capable of detecting the known subtle structural phase transition in PrNiO$_3$ at 120 K, while no transitions were detected in the LaNiO$_3$ sample at low temperatures. Furthermore, a newly introduced analysis technique for LD data allows us to account for resolution effects that originate from small angle scattering from powder samples.
