Structural and Magnetic Investigations for the Doping Effect of Nonmagnetic Impurity on the Spin-Peierls-like Transition in a Quasi-One-Dimensional Magnet: 1-(4‘-Nitrobenzyl)pyridinium Bis(maleonitriledithiolato)nickelate

A nonmagnetic compound, [NO2BzPy][Au(mnt)2] (NO2BzPy+ = 1-(4‘-nitrobenzyl)pyridinium; mnt2- =
maleonitriledithiolate), was synthesized and characterized structurally, which is isostructural with [NO2BzPy][Ni(mnt)2] that is a quasi-one-dimensional magnet and possesses a spin-Peierls-like transition with J = 192
K in the gapless state and spin energy gap = 738 K in the dimerization state, respectively. Further, ten
nonmagnetic impurity doped compounds with a formula [NO2BzPy][AuxNi1-x(mnt)2] (x = 0.01−0.73) were
prepared and investigated by crystal structural determinations and magnetic susceptibility measurements. The
nonmagnetic doping causes the suppression of the spin transition with an average rate of 221(12) K/percentage
of dopant concentration. From the plots of χm−T, the transition collapse (the characteristic of the transition
is the sudden drop of χm upon cooling, and the disappearance of this characteristic is considered as the criterion
for the transition collapse) is estimated at around x > 0.27. In heavier doped system x = 0.49, the spin gap
vanishes and a gapless phase is achieved again.