  We explore the influence of demagnetization interaction on magnetic memory
effect by varying organization geometry of anisotropic ZnFe$_2$O$_4$
nanoparticles in an ensemble. The static and dynamic behaviour of two
differently organized ensembles, compact ensemble (CE) and hollow core ensemble
(HCE), are extensively studied by both dc and ac susceptibility, magnetic
memory effect and spin relaxation. The frequency-dependence peak shifting of
freezing temperature in both the systems is analyzed properly with the help of
two dynamic scaling models: Vogel-Fulcher law and power law. Presence of
cluster spin-glass phase is reflected from Vogel-Fulcher temperature $T_0$
$\simeq$ 142.58 K for CE, $\simeq$ 97 K for HCE and characteristic time
constant $\tau_0$ $\simeq$ $8.85\times10^{-9}$ s for CE, $\simeq$
$3.8\times10^{-10}$ s for HCE; along with $\delta$T$_{Th}$ $\sim$ 0.1 for CE
and 0.2 for HCE. The power law fitting with dynamic exponent $zv'$ = 6.2 $\pm$
1.1 for CE, 6.3 $\pm$ 0.5 for HCE and single spin flip $\tau^*$ $\simeq$
$7.7\times10^{-11}$ s for CE, $\simeq$ $1.3\times10^{-10}$ s for HCE provide
firm confirmation of cluster spin-glass phase. The progressive spin freezing
across multiple metastable states with prominent memory effects is reflected in
both the systems via nonequilibrium dynamics study. The hollow core geometry
with anisotropic nanoparticles on surface with closer proximity leads to
complex anisotropy energy landscape with enhanced demagnetizing field resulting
highly frustrated surface spins. As a consequence, more prominent magnetic
memory effect is observed in HCE with higher activation energy, reduced
blocking temperature and enhanced coercivity than that of CE.
