Chiral Magnetic Crystals

We discuss a new class of magnetic systems, chiral magnetic crystals [1]. One speaks of chirality when a system exists in two versions (enantiomorphs) that cannot be superposed upon each other by proper (pure) rotations C. Ordinarily, this is tantamount to the case that the enantiomorphs are mirror images of each other, i.e., the enantiomorphs are mapped onto each other by improper rotations iC, where i denotes space inversion. We call this case electrochirality because it arises from electric multipolar order. By treating space inversion i, time inversion θ, and their combination iθ on the same footing, we identify magnetochirality and antimagnetochirality as new categories of chirality characterized by the existence of two distinct enantiomorphs. In multichiral systems, all these inversion symmetries are absent so that these systems have four distinct enantiomorphs. The new forms of chirality identified here are caused by magnetic multipole order; they are realized in magnetic crystals. We discuss material examples and comment on their novel properties. [1] arxiv:2405.20940.