Editorial: Altermagnetism—A New Punch Line of Fundamental Magnetism

Altermagnetism-A New Punch Line of Fundamental MagnetismNon sunt multiplicanda entia sine necessitate, entities should not be multiplied without necessity.This observation made by the Franciscan monk John Punch in 1639 [1] still resonates with one of PRX's editorial philosophies: new terminology should only be introduced into papers when it advances understanding.Yet, the second Perspective article we have invited and are now publishing [2] seems to have done just the opposite.It introduces a new term into the century-old field of magnetism: "altermagnetism."PRX's authors and readers could rightly ask: Why make an exception here?Let us now take a step back.Interesting magnetic patterns have long been a core topic in condensed matter physics.This interest has intensified during the recent decades, not least because of a growing interest in spintronics.New terms, such as skyrmion orders, have been introduced that justifiably deserve their separate drawers in the nomenclature chest, as they do label and signify new physics.What has been lacking, in our opinion, is a comprehensive classification of different magnetic orders, preferably based on symmetry criteria and observable manifestations.In complement to the Perspective, we present such a classification scheme in Fig. 1.We believe that altermagnetism, describing an array of qualitatively novel phenomenology that has emerged during the past few years, now merits its own drawer.