Synthesis and characterization of single crystal and polycrystalline La3Ni2O7-δ

Abstract

Recent observation of superconductivity in La₃Ni₂O_7-δ have sparked renewed interest in high-temperature superconductors. Despite years of research, challenges with existing samples have raised questions about their intrinsic features, demanding on exploring new synthesis routes on this material. In this study, single crystals of La₃Ni₂O_7-δ were grown using CsCl flux for the first time, while polycrystalline synthesis was explored through solid-state reaction. The electrical resistivity of the polycrystalline samples showed an insulating behavior, whereas the single crystals exhibited metallic behavior with an anomaly at T∗ ∼110 K, likely due to a density wave order. A distinct V-shaped magnetoresistance is observed at temperatures below T∗ in a single crystal sample. Furthermore, Raman spectroscopy of the single crystals highlights prominent phonon modes, reflecting the complex bilayer structure of La₃Ni₂O_7-δ. These findings emphasized a new synthesis route for La₃Ni₂O_7-δ and highlight the influence of synthesis conditions on its magnetic and electronic properties.