Colossal magnetoresistance - Not just a load of bolometers

The electrical resistance of certain materials changes enormously in a magnetic field. It has been hard to explain the magnitude of this 'colossal magnetoresistance'; but now in one group of materials — the cubic manganese perovskites — a partial explanation may have been found. In the conducting state, there is a sea of electrons, much as there is in a metal; in the high-resistance state, the current-carrying electrons are localized at atomic sites. Current can still flow, but the movement of electrons causes a physical distortion, and it appears to be this distortion that makes the resistance so high.