Evidence for charge and spin density waves in single crystals of La3Ni2O7 and La3Ni2O6

Charge and spin order is intimately related to superconductivity in copper oxide superconductors. To elucidate the competing orders various nickel compounds are crucial given fact that has been discovered Nd$_{0.8}$Sr$_{0.2}$NiO$_2$ films. Herein, we report structural, electronic transport, magnetic, thermodynamic characterizations on single crystals of La$_3$Ni$_2$O$_7$ La$_3$Ni$_2$O$_6$. metallic with mixed Ni$^{2+}$ Ni$^{3+}$ valent states. Resistivity measurements yield two transition-like kinks at $\sim$110 153 K, respectively. The kink K further revealed from magnetization specific heat measurements, indicative formation charge order. La$_3$Ni$_2$O$_6$ obtained topochemical reduction insulating show an anomaly $\sim$176 magnetic susceptibility. behaviors analogous observed La$_4$Ni$_3$O$_{10}$ La$_4$Ni$_3$O$_8$, suggesting a common feature ternary La-Ni-O system mixed-valent states nickel.