  Magnetic hopfions are topologically protected three-dimensional solitons that
are constituted by a tube which exhibits a topologically nontrivial spin
texture in the cross-section profile and is closed to a torus. Here we show
that the hopfion's locally uncompensated emergent field leads to a topological
Hall signature, although the topological Hall effect vanishes on the global
level. The topological Hall signature is switchable by magnetic fields or
electric currents and occurs independently of the anomalous and conventional
Hall effects. It can therefore be exploited to electrically detect hopfions in
experiments and even to distinguish them from other textures like skyrmion
tubes. Furthermore, it can potentially be utilized in spintronic devices.
Exemplarily, we propose a hopfion-based racetrack data storage device and
simulate the electrical detection of the hopfions as carriers of information.
