Competing Charge/Spin-Stripe and Correlated Metal Phases in Trilayer Nickelates (Pr_1–<i>x</i>La_<i>x</i>)₄Ni₃O₈

Low valent nickelates Rn+1NinO2n+2 (R = rare earth) containing Ni1+ (d9) with a quasi-two-dimensional (quasi-2D) square-planar coordination geometry possess structural and electronic properties that are similar to those of high Tc cuprates, including superconductivity itself in the doped infinite-layer (n ?) RNiO2 system. Within this nickelate family, crystallographic isomorphs Pr4Ni3O8 La4Ni3O8 exhibit singularly different ground states: is metallic, charge- spin-stripe-ordered insulator. To explore understand state evolution from metallic stripe-ordered R4Ni3O8 we have grown series isovalent, substituted single crystals (Pr1–xLax)4Ni3O8. Combining thermodynamic, transport, magnetic, synchrotron X-ray crystal diffraction measurements, reveal T 0 transition between stripe-insulator phase regions, putative quantum at x ? 0.45. We propose two possible models for (Pr1–xLax)4Ni3O8: an electronically inhomogeneous system could serve as candidate exploring Griffiths physics or homogeneous clean critical point boundary.