Dissipationless Current in Magnets

As the magnetic sample is made increasingly dirty, the normal current (dark arrows) is degraded. However, the Hall current (light arrows) is unaffected.

IRG 1: W.-L. Li, S. Watauchi, V.L. Miller, R.J. Cava, and N.P. Ong

Normally, an electric current flowing in metals and semiconductors is strongly degraded (dissipated) by the scattering of the electrons from trace impurities. Theorists have long suspected that the Hall current observed in all magnetic materials may be a striking exception, i.e. it has the same value regardless of the impurity content in the sample (the Hall current flows perpendicular to the applied electric field). Such a ‘dissipationless’ current may find applications in a new generation of electronic devices based on the spin of the electron.

Recently, a team of scientists at Princeton University have confirmed this 50-year old prediction by showing that the Hall current in a magnet is indeed dissipationless - unchanging despite a large increase in the impurity concentration. In removing a major obstacle to our understanding of the quantum mechanical behavior of electrons inside magnets, the Princeton experiment improves the prospects of realizing high-speed electronics that generate much less heat than present-day devices.

Related publication [DMR-0213706]:
W.L. Li, S. Watauchi, V.L. Miller, R.J. Cava, and N.P. Ong, "Dissipationless Anomalous Hall Current in the Ferromagetic Spinel CuCr₂Se_4-xBr_x", Science 303, 1647 (2004).