Where two oppositely magnetized regions meet, there is a so-called domain wall. Under the right conditions, this wall can be made to oscillate like a pendulum, suggesting a new approach to electronics. On page 203 of this issue, Saitoh et al. providea beautiful demonstration of a magnetic domain wall oscillating just as a pendulum would do under gravity. A domain wall separates two uniformly magnetized regions and is predicted, at low excitation energies, to behave like a particle with a finite mass. By trapping a single magnetic domain wall in a strip of ferromagnetic material, Saitoh et al. show that they can force the oscillations of the wall inside this potential well, achieving resonant displacements of micrometre length at megahertz frequencies -- all with only moderate currents, a key result for possible applications.
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