Altermagnetism and Kinetomagnetism

Sang-Wook Cheong

Keck Center for Quantum Magnetism, Rutgers University, NJ, USA

Altermagnetism is introduced as a category of magnetic states with ‘collinear’ antiferromagnetic spins and alternating variations of local structures around spins in such a way that the symmetry allows typical ferromagnetic behaviors. Altermagnets exhibiting

ferromagnetic behaviors without any external perturbations (type-I) turn out to belong to the ferromagnetic point group. Other altermagnets (type-II and type-III) can have ferromagnetic behaviors only with external perturbations such as electric current or stress, which conserve parity-time-reversal (PT) symmetry. All types of altermagnets themselves have broken PT symmetry. The concept of altermagnetism can be extended to accommodate non-collinear spins and multiple local-structure variations. All these altermagnets are classified in terms of magnetic point groups.

Kinetomagnetism refers to magnetization induced by electric current, encompassing longitudinal or transverse effects and even- or odd-order effects. The precise relationship between Altermagnetism and Kinetomagnetism warrants exploration.

The intersection of Altermagnetism and Kinetomagnetism presents both opportunities and challenges in science and technology.

References

• [1] Chen, H., Niu, Q. & Macdonald, A. H. Anomalous Hall effect arising from noncollinear antiferromagnetism. Phys. Rev. Lett. 112, 017205 (2014).
• [2] Šmejkal, L., Sinova, J. & Jungwirth, T. Emerging research landscape of altermagnetism. Phys. Rev. X 12, 040501 (2022).
• [3] Cheong, S-W. and Huang F-T., Altermagnetism with Non-collinear Spins, npj Quantum Materials 9, 13 (2024).