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'colossal' Magnetic Effect Under Pressure


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Scientists are on the verge of understanding and controlling the colossal magnetoresistance effect (CMR), a phenomenon that is potentially up to a thousand times more powerful than the giant magnetoresistance effect and could result in a major revolution in computing technology. However, understanding and controlling this effect, which involves the intricate coupling between electrical conductivity and magnetism, remains a major challenge because of competing interactions in manganites, the materials in which CMR was discovered.

A team of researchers led by Yang Ding of the Carnegie Institution's High Pressure Synergetic Center are studying the magnetic properties of manganites, a form of manganese oxide, using applied techniques called x-ray magnetic circular dichroism and angular-dispersive diffraction at the Advanced Photon Source of Argonne National Laboratory. The discovery of CMR in manganite compounds has already made manganites important in technological applications, such as magnetic tunneling junctions in magnetic random access memory (MRAM), which will be released in the near future. Unlike traditional RAM, MRAM could be used in instant-on computers.

However, there are currently no theories that explain the physics, including CMR effects, seen in manganites. "The challenge is that there are competing interactions in manganites among the electrons that determine magnetic properties," Ding says. "And the properties are also affected by external stimuli, such as temperature, pressure, magnetic field, and chemical doping."

From Carnegie Institution for Science
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