  The NiO4 plaquettes in La2NiO4.17, a cousin of the hole-doped
high-temperature superconductor La{2-x}SrxCuO4, have been studied by 61Ni-NMR
in 14 T in a single crystal enriched in 61Ni. Doped and undoped plaquettes are
discriminated by the shift of the NMR resonance, leading to a small line
splitting, which hardly depends on temperature or susceptibility. The smallness
of the effect is additional evidence for the location of the holes as deduced
by Schussler-Langenheine et al., Phys. Rev. Lett. 95, 156402 (2005). The
increase in linewidth with decreasing temperature shows a local field
redistribution, consistent with the formation of charge density waves or
stripes. For comparison, we studied in particular the grandmother of all planar
antiferromagnets K2NiF in the paramagnetic state using natural abundant 61Ni.
The hyperfine fields in both 2-dimensional compounds appear to be remarkably
small, which is well explained by super(transferred) hyperfine interaction. In
K2NiF4 the temperature dependence of the susceptibility and Knight shift cannot
be brought onto a simple scaling curve. This unique feature is ascribed to a
different sensitivity for correlations of these two parameters.
