Substitution and cointercalation effects on superconducting electron-doped layer structured metal nitride halides

The effects of substitution of halogens and metals in β-MNX (M = Zr, Hf; X = CI, Br, I) on the superconductivity of the electron-doped compounds were studied. The onset temperature (Tc) was mainly determined by the type of nitride layers (ZrN or HfN), and varied linearly with the compositions between the Tcs of the end members. The post-cointercalation of propylene carbonate molecules with Na greatly expanded the spacing between the nitride layers without changing the doping level and the two-dimensional structure. The cointercalation phase had irreversible temperature in the magnetization curves, and showed an anisotropic effect on Tc and the magnetic susceptibility.