Phase formation in hole- and electron-doped rare-earth nickelate single crystals

The recent discovery of superconductivity in hole-doped infinite-layer nickelates has triggered a great interest in the synthesis of novel nickelate phases, which have primarily been examined in thin film samples. Here, we report the high-pressure optical floating zone (OFZ) growth of various perovskite and perovskite-derived rare-earth nickelate single-crystals, and investigate the effects of hole-, electron-, and self-doping. For hole-doping with Ca and Sr, we observe phase separations during the growth process when a substitution level of 8% is exceeded. A similar trend emerges for electron-doping with Ce and Zr. Employing lower doping levels allows us to grow sizeable crystals in the perovskite phase, which exhibit significantly different electronic and magnetic properties than the undoped parent compounds, such as a decreased resistivity and a suppressed magnetic response. Our insights into the doping-dependent phase formation and the resulting properties of the synthesized crystals reveal limitations and opportunities for the exploration and manipulation of electronic states in rare-earth nickelates.

Automated summary

The discovery of superconductivity in hole-doped infinite-layer nickelates has spurred interest in synthesizing novel nickelate phases, mostly examined in thin film samples. In this study, we report the growth of various perovskite and perovskite-derived rare-earth nickelate single-crystals using high-pressure optical floating zone (OFZ) method, and investigate the effects of different types of doping. Our results show phase separations during growth process when a substitution level of 8% is exceeded for hole-doping with Ca and Sr, and similar trends for electron-doping with Ce and Zr. By employing lower doping levels, we are able to grow large crystals in the perovskite phase, which exhibit distinct electronic and magnetic properties compared to undoped parent compounds.