  Crystalline Mn5Ge3 nanomagnets are formed inside a Mn-diluted Ge matrix using
Mn ion implantation. A temperature-dependent memory effect and slow magnetic
relaxation are observed below the superparamagnetic blocking temperature of
Mn5Ge3. Our findings corroborate that the observed spin-glass-like features are
caused by the size distribution of Mn5Ge3 nanomagnets, rather than by the
inter-particle interaction through the Mn-diluted Ge matrix.
