Abstract
The ac susceptibility measurement probes the dynamic properties of a magnetic material,
which is believed to consist of magnetization rotation and domain wall motion contributions.
Here we report the observation of a complete quenching of the initial ac susceptibility for a
single domain Ni nanobar array, when the ac field is aligned with the long axis of the bars. The
vanishing of the susceptibility in one direction is a unique nanoscale phenomena, allowing an
unambiguous determination of the magnetic state of the nanostructure and a clean separation of
different contributions to its dynamic properties. For example, an unambiguous determination
of the surface anisotropy energy is obtained when the field is applied perpendicular to the long
axis.
