  Relaxor-ferroelectrics display exceptional dielectric properties resulting
from the underlying random dipolar fields induced by strong chemical
inhomogeneity. An unusual structural aspect of relaxors is a skin-effect where
the near-surface region in single crystals exhibit structures and critical
phenomena that differ from the bulk. Relaxors are unique in that this skin
effect extends over a macroscopic lengthscale of $\sim$ 100$\mu$m whereas usual
surface layers only extend over a few unit cells (or $\sim$ nm). We present a
muon spectroscopy study of Pb(Fe$_{1/2}$Nb$_{1/2}$)O$_{3}$ (PFN) which displays
ferroelectric order, including many relaxor-like dielectric properties such as
a frequency broadened dielectric response, and antiferromagnetism with
spatially short-range polar correlations and hence can be termed a
multiferroic. In terms of the magnetic behavior determined by the Fe$^{3+}$
($S=5/2$, $L\approx0$) ions, PFN has been characterized as a unique example of
a "cluster spin-glass". We use variable momentum muon spectroscopy to study the
depth dependence of the slow magnetic relaxations in a large 1 cm$^{3}$ crystal
of PFN. Zero-field positive muon spin relaxation is parameterized using a
stretched exponential, indicative of a distribution of relaxation rates of the
Fe$^{3+}$ spins. This bandwidth of frequencies changes as a function of muon
momentum, indicative of a change in the Fe$^{3+}$ relaxation rates as a
function of muon implantation depth in our single crystal. Using negative muon
elemental analysis, we find small-to-no measurable change in the
Fe$^{3+}$/Nb$^{5+}$ concentration with depth implying that chemical
concentration alone cannot account for the change in the relaxational dynamics.
PFN displays an analogous magnetic skin effect reported to exist in the
structural properties of relaxor-ferroelectrics.
