D. Markgraber et G. Engelhardt, K-39 MAS NMR of KNiF3: unexpected spin density at the potassium and first MAS NMR experiments in the antiferromagnetic state, CHEM P LETT, 300(5-6), 1999, pp. 701-705
K-39 MAS NMR spectra of KNiF3 were measured at variable temperature between
180 and 450 K, In the paramagnetic state (450-270 K), a shift of the K-39
resonance to lower frequency is observed with decreasing temperature which
is due to an isotropic hyperfine interaction with A(iso) = -(0.30 +/- 0.05)
x 10(-6) cm(-1). This is in contrast to theory which predicts zero unpaire
d electron density at the potassium. In the antiferromagnetic state (below
250 K), a reduction of the shift contribution from the unpaired electrons i
s observed. The temperature dependence of the K-39 shifts parallels that of
the magnetic susceptibilities over the whole temperature range measured. (
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