Magnetism can decline drastically when put under pressure

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Washington, Jan 30 : Scientists have discovered that the magnetic strength of magnetite-the most abundant magnetic mineral on Earth-declines drastically when put under pressure.

This finding was made by researchers from the Carnegie Institution's Geophysical Laboratory, together with colleagues at the Advanced Photon Source of Argonne National Laboratory in the US.

According to the research, when magnetite is subjected to pressures between 120,000 and 160,000 times atmospheric pressure, its magnetic strength declines by half. This change is due to what is called electron spin pairing.

Magnetism comes from unpaired electrons in magnetic materials. The strength of a magnet is a result of the spin of unpaired electrons and how the spins of different electrons are aligned with one another.

This research showed that the drop in magnetism was due to a decrease in the number of unpaired electrons.

To study the mineral, the researchers developed and applied a novel technique, called X-ray Magnetic Circular Dichroism (XMCD) at the Advanced Photon Source, a high-energy synchrotron facility. The technique uses high-brilliance circularly polarized X-rays to probe the magnetic state of magnetite as a diamond anvil cell subjects a sample to many hundreds of thousands of atmospheres.

The researchers combined their experimental results with theoretical calculations by collaborators to pinpoint why the magnetic strength changes.

According to the research, the electron-spin configuration in the iron sites of the mineral is to be blamed for the origin of the phenomenon.

This discovery not only shows the profound effects of pressure on magnetism, it also discloses, for the first time, that pressure induced a spin pairing transition that results in changes in the electron mobility and structure.

"The discovery is important," said Yang Ding, the study's lead author. "It advances our understanding of the correlation of magnetism, electron transport, and structural stability in materials with strong electron interactions, like magnetite," he added.

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