A Magnetic Hall Effect in the Nonmagnetic Phase of an Ultraclean Metal

What is it about?

For over a century, the electronic transport effect known as the anomalous Hall effect was thought to be a property of ferromagnetic metals, such as iron, reflecting their inherent magnetization. More recently, this important effect has been found in antiferromagnets, despite their minimal net magnetization. In this work, the authors show that an antiferromagnetic complex palladium chromium oxide material with ultrahigh conductivity not only exhibits the anomalous Hall effect, but does so at up to seven times the magnetic ordering temperature, i.e., while the material is in its "nonmagnetic" phase. The work shows that this is directly linked to a wide temperature range where the chromium spins are strongly correlated on short scales, but are unable to order due to their triangular lattice in this material. These spin correlations are measured directly by scattering neutrons from the material, establishing clear correlations with the electronic transport effects.

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Photo by Pawel Czerwinski on Unsplash

Photo by Pawel Czerwinski on Unsplash

Why is it important?

Obtaining such a magnetic Hall effect above the magnetic ordering temperature of the material, and elucidating its origin, is significant, as it points to a potential path for room-temperature effects even in low-temperature antiferromagnets. The work also further underscores the potential of the fascinating class of materials known as metallic delafossites. These materials exhibit ultraclean, low-disorder electronic transport, amplifying interesting physical phenomena and revealing new ones.

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