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arXiv · 1803.00217

Theory of orbital magnetic quadrupole moment and magnetoelectric susceptibility

Atsuo Shitade·Hikaru Watanabe·Youichi Yanase
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Abstract

We derive a quantum-mechanical formula of the orbital magnetic quadrupole moment (MQM) in periodic systems by using the gauge-covariant gradient expansion. This formula is valid for insulators and metals at zero and finite temperature. We also prove a direct relation between the MQM and magnetoelectric (ME) susceptibility for insulators at zero temperature. It indicates that the MQM is a microscopic origin of the ME effect. Using the formula, we quantitatively estimate these quantities for room-temperature antiferromagnetic semiconductors BaMn$_2$As$_2$ and CeMn$_2$Ge$_{2 - x}$Si$_x$. We find that the orbital contribution to the ME susceptibility is comparable with or even dominant over the spin contribution.

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Atsuo Shitade, Hikaru Watanabe, Youichi Yanase. 2018-07-16. Theory of orbital magnetic quadrupole moment and magnetoelectric susceptibility. https://doi.org/10.1103/physrevb.98.020407

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