When you place a magnetic dipole, such as an electron or a ferromagnetic domain, in a magnetic field, it will align with the field. It will, however, not be able to do so instantaneously: To reach the new magnetization direction, it will have to spin about the field axis, a process called precessional motion that is gradually opposed by damping. In 1956, Kikuchi gave the first theoretical answer to the question of the minimum time needed to reverse a dipole owing to this damped precessional motion. But more than 40 years had to elapse before the minimal field strength required for precessional magnetization reversal could be evaluated experimentally.
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