X-ray study of ferroic octupole order producing anomalous Hall effect

Recently found anomalous Hall, Nernst, magnetooptical Kerr, and spin Hall effects in the antiferromagnets Mn3X (X = Sn, Ge) are attracting much attention for spintronics and energy harvesting. Since these materials are antiferromagnets, the origin of these functionalities is expected to be different from that of conventional ferromagnets. Here, we report the observation of ferroic order of magnetic octupole in Mn3Sn by X-ray magnetic circular dichroism, which is only predicted theoretically so far. The observed signals are clearly decoupled with the behaviors of uniform magnetization, indicating that the present X-ray magnetic circular dichroism is not arising from the conventional magnetization. We have found that the appearance of this anomalous signal coincides with the time reversal symmetry broken cluster magnetic octupole order. Our study demonstrates that the exotic material functionalities are closely related to the multipole order, which can produce unconventional cross correlation functionalities. The X-ray magnetic circular dichroism detection of magnetic octupole moment has not been experimentally demonstrated so far. Here, the authors observe ferroic order of magnetic octupole in Mn3Sn, finding the exotic material functionalities related to the multipole order.

Automated summary

The observation of ferroic order of magnetic octupole in Mn3Sn by X-ray magnetic circular dichroism, which has only been predicted theoretically so far, indicates that the exotic material functionalities are closely related to the multipole order. The decoupling of observed signals from uniform magnetization suggests that X-ray magnetic circular dichroism in Mn3Sn is not originating from conventional magnetization, pointing to the possibility of unconventional cross correlation functionalities due to multipole order. The detection of magnetic octupole moment through X-ray magnetic circular dichroism has not been experimentally demonstrated before.