Impurity doping to molecular spin ladders: Magnetic properties of p-EPYNN+center dot[Ni(dmit)(2)](-)(1-x) [Au(dmit)2](-)(x)

We studied impurity effects on the magnetic properties of p-EPYNN+.[Ni(dmit )(2)](-) (p-EPYNN+ = p-N-ethylpyridinium nitronylnitroxide and [Ni(dmit)(2) ] (dmit=1, 3-dithiol-2-thione-4, 5-dithiolate), whose crystal involved a mo lecular spin ladder of [Ni(dmit)(2)](-) sandwiched by side-by-side and head -to-tail stacking chains of p-EPYNN+, by means of partial replacement of pa ramagnetic [Ni(dmit)(2)](-) with non-magnetic [Au(dmit)(2)](-). In the soli d solutions, p-EPYNN+.[Ni(dmit)(2)](-)(1-x)[Au(dmit)(2)](-)(x), an increase in x results in an increase of paramagnetic lattice defects on the spin la dder of [Ni(dmit)(2)](-), which become pathes of an antiferromagnetic inter action between the ferromagnetic chains of p-EPYNN+.