Magnetoresistance from quantum interference effects in ferromagnets (vol 404, pg 581, 2000)

The desire to maximize the sensitivity of read/write heads (and thus the in formation density) of magnetic storage devices has stimulated interest in t he discovery and design of new magnetic materials exhibiting magnetoresista nce. Recent discoveries include the 'colossal' magnetoresistance in the man ganites(1-4) and the enhanced magnetoresistance in low-carrier-density ferr omagnets(4-6). An important feature of these systems is that the electrons involved in electrical conduction are different from those responsible for the magnetism. The latter are localized and act as scattering sites for the mobile electrons, and it is the field tuning of the scattering strength th at ultimately gives rise to the observed magnetoresistance. Here we argue t hat magnetoresistance can arise by a different mechanism in certain ferroma gnets-quantum interference effects rather than simple scattering. The ferro magnets in question are disordered, low-carrier-density magnets where the s ame electrons are responsible for both the magnetic properties and electric al conduction. The resulting magnetoresistance is positive (that is, the re sistance increases in response to an applied magnetic field) and only weakl y temperature-dependent below the Curie point.