Beyond Conventional Ferromagnetism and Antiferromagnetism: A Phase with Nonrelativistic Spin and Crystal Rotation Symmetry Article Swipe
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· 2022
· Open Access
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· DOI: https://doi.org/10.1103/physrevx.12.031042
· OA: W4297014776
The search for novel magnetic quantum phases, phenomena and functional\nmaterials has been guided by relativistic magnetic-symmetry groups in coupled\nspin and real space from the dawn of the field in 1950s to the modern era of\ntopological matter. However, the magnetic groups cannot disentangle\nnon-relativistic phases and effects, such as the recently reported\nunconventional spin physics in collinear antiferromagnets from the typically\nweak relativistic spin-orbit coupling phenomena. Here we discover that more\ngeneral spin symmetries in decoupled spin and crystal space categorize\nnon-relativistic collinear magnetism in three phases: conventional ferromagnets\nand antiferromagnets, and a third distinct phase combining zero net\nmagnetization with an alternating spin-momentum locking in energy bands, which\nwe dub "altermagnetic". For this third basic magnetic phase, which is omitted\nby the relativistic magnetic groups, we develop a spin-group theory describing\nsix characteristic types of the altermagnetic spin-momentum locking. We\ndemonstrate an extraordinary spin-splitting mechanism in altermagnetic bands\noriginating from a local electric crystal field, which contrasts with the\nconventional magnetic or relativistic splitting by global magnetization or\ninversion asymmetry. Based on first-principles calculations, we identify\naltermagnetic candidates ranging from insulators and metals to a parent crystal\nof cuprate superconductor. Our results underpin emerging research of quantum\nphases and spintronics in high-temperature magnets with light elements,\nvanishing net magnetization, and strong spin-coherence.\n
