Colossal magnetoresistance is aptly named. By subjecting a piece of appropriately doped manganite to a strong magnetic field and a moderately low temperature, one can raise its electrical conductivity by orders of magnitude.

Despite its prodigious magnitude, CMR has not led to any commercial devices since its discovery 15 years ago. Cooling a sample by the requisite few tens of kelvin isn’t hard, but it is inconvenient for manufacturers. Worse, CMR shows up only at the mighty, tesla-scale magnetic fields used in magnetic resonance imaging scanners.

To physicists, however, CMR remains intriguing. Unlike its already commercialized cousins, giant magnetoresistance and tunneling magnetoresistance, CMR doesn’t rely on the nanoscale layering of different materials. It’s an intrinsic property of a single substance. Depending on the doping level and external conditions, a CMR material can be a ferromagnetic metal, a paramagnetic insulator, or an antiferro-magnetic insulator in which the valence electrons arrange themselves...

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