Key mechanism behind the Colossal Magneto-Resistance effect in the Manganites

The manganites are known to exhibit colossal magneto-resistance effects. Using state-of-the-art electron microscopy techniques we were able to reveal the key mechanism, polaron melting and ordering, that underlies the intriguing physical behavior of these materials. Polaron excitations in a crystalline material are dynamic lattice vibrations that accompanying a moving charge carrier as it travels through the crystal lattice. In manganites, this lattice distortion can strongly affect the electrical and magnetic properties of the material, yet the interaction is poorly understood. By imaging and spectrally analyzing manganite crystals on the atomic scale while simultaneously applying a local electric current, it was possible to directly observe colossalresistance effects reflecting a solid-liquid transition in the polaron-ordered state of the manganite. Combined with the spectroscopy data that helped reveal bonding-electron excitations, this lead to a detailed structural model of the polaron-ordered and -disordered states. The models reveal atomic positions, displacements, polarizations, and magnetic-spin directions responsible for the physical properties and behavior of the material, which has the possibility of strongly impacting the development of correlated-electron devices.