Zn-barlowite exhibits a layered structure in which copper ions within each layer form
a kagome lattice. The complex magnetic behavior of this compound originates from
impurities in which copper ions partially substitute the out-of-plane zinc sites. In
quantum spin liquids, for which the studied material is considered a candidate, such
impurities generate spin-polarized domains that influence the intrinsic magnetic pro-
perties, particularly in the low-temperature regime. Their temperature-dependent
magnetic response introduces uncertainty in determining the actual impurity con-
centration and raises the fundamental question of whether a spin gap is present in
the ground state. Fluorine ions located between the kagome layers provide a suita-
ble local probe for investigating the material using nuclear magnetic resonance (19F
NMR). In this study, we employed a two-component model to resolve two distinct
local environments from the 19F signal: the intrinsic kagome component and the
component associated with Cu2+ impurities. By fitting the model and performing
a global optimization of parameters across the temperature range from 2 K to 110
K, we determined the impurity concentration in the analyzed samples. Using the
obtained information on the sample composition, we further investigated the spin
dynamics by measuring and analyzing the spin–lattice relaxation time T1 within a
two-component framework. The results reveal a longer relaxation time of the intrin-
sic component than predicted for an ideal kagome antiferromagnet, suggesting the
absence of a homogeneous spin gap. However, since the 19F NMR signal averages
over many surrounding spins, a definitive conclusion regarding the presence of a spin
gap cannot be drawn, as possible spatial inhomogeneities may be averaged out by
the method. Nevertheless, this study demonstrates an effective analytical appro-
ach that improves the interpretability of local-probe NMR measurements in systems
where multiple local environments with distinct magnetic properties coexist.
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