Crystal Structure and Magnetic Properties of the S=1 Quasi-One-Dimensional Compound Ni([15]aneN₄)N₃(PF₆)

Abstract

A new S=1 quasi-one-dimensional compound Ni([15]aneN₄)N₃(PF₆) (chemical formula NiC₁₁N₇H₂₆PF₆, in short NPAP) has been synthesized. Both crystal structure and magnetic properties of this compound have been characterized using the single crystal samples. NPAP crystallizes in the orthorhombic system, with space group P2nn (No. 34), Z=2 and unit-cell parameters a=11.332(5)Å, b=13.861(4)Å and c=6.173(2)Å, respectively. The crystal structure was solved using direct method and the refinement converged at R(R_w)=0.062(0.062). A superlattice along the c-axis was conformed by both X-ray Weissenberg film and powder diffraction method. In addition, a disorder of the packing sequence of the ([15]aneN₄) in-plane ligands along the c-axis was proposed. The temperature dependence of magnetization of a single crystal of NPAP was measured using a SQUID magnetometer. We have observed a large difference in zero field cooled and field cooled magnetizations below about 20K. We have also measured the AC susceptibility of this sample in zero static magnetic field. A cusp is observed at about 22K in the temperature dependence of AC susceptibility.