Periodic Reporting for period 1 - ALTERMAG (Altermagnetism and spintronics without magnetization and relativity)
Reporting period: 2023-10-01 to 2026-03-31
Magnetically ordered crystals are traditionally divided into two basic phases -- ferromagnetism and antiferromagnetism. The ferromagnetic order offers a range of phenomena and device applications. The vanishing net magnetization in antiferromagnets is potentially favorable for spatial and temporal scalability of devices. Recently, our team and others have predicted instances of strong time-reversal symmetry breaking and spin splitting in electronic bands, typical of ferromagnetism, in crystals with antiparallel compensated magnetic order, typical of antiferromagnetism. Our central idea, resolving this apparent fundamental conflict in magnetism, is that symmetry classifies a third basic magnetic phase. Its alternating spin polarizations in both crystal-structure real space and electronic-structure momentum space suggest a term altermagnetism. We will demonstrate that altermagnets combine merits of ferromagnets and antiferromagnets, that were regarded as principally incompatible, and have merits unparalleled in either of the two traditional basic magnetic phases. In Objective 1 we will establish materials landscape of altermagnetism and, in Objective 2, show how its anisotropic (d-wave) nature enriches fundamental physics concepts of ordered phases in condensed matter. This will underpin our development of a new avenue in spintronics, elusive within the two traditional magnetic phases, based on strong non-relativistic spin-conserving phenomena, without magnetization imposed scalability limitations, and with complex functionalities. The demonstration of altermagnetic spintronic functionalities and devices are the Objectives 3 and 4 of the project.
Prior to the ALTERMAG project, the PI’s team was intensely searching for the existence of a hitherto unknown class of magnets that would combine the advantages of ferromagnets and antiferromagnets. Specifically, the team searched for substances that could enable the generation of strong conserved spin currents, like in conventional ferromagnets, while featuring a vanishing magnetization, like in conventional antiferromagnets. Such properties were traditionally considered in physics as mutually exclusive. The research led to the prediction of altermagnets whose exploration is the topic of ALTERMAG.
The anisotropic higher-partial-wave ordering in altermagnets bears physical analogies to the higher-partial-wave ordering in unconventional superfluidity and superconductivity discovered in the 1970s and 1980s. The founders of quantum mechanics have been asking questions about whether such unconventional phases can in principle exist since the 1940s. In superfluidity/superconductivity they were discovered a few decades later, while it took another several decades before the magnetic counterparts were eventually discovered by the PI and collaborators in the form of altermagnetism. Within two years preceding the ALTERMAG project, the PI and collaborators published predictions of the anomalous Hall effect and other spintronic phenomena in altermagnets. Between the submission and the starting date of ALTERMAG, two key works followed. The first one focused on a basic theoretical delineation and description of altermagnetism, and the second one on the broad potential of this unconventional magnetic phase in science and technology. During the first reporting period of the project, the experimental researched started from observations of the anomalous Hall effect. The ALTERMAG team then coordinated research which provided the decisive spectroscopic experimental evidence of altermagnetism. The discovery attracted extraordinary attention not only in the scientific community. Popular articles about altermagnets as a third distinct basic class of magnets were published, among others, in Science, Nature, ScienceNews, The Economist, Newsweek, or The Financial Times. Further spectroscopic evidence of altermagnetism was then provided by the PI and collaborators. In parallel, the prediction and observation of circular dichroism opened a direct way for microscopic imaging of the altermagnetic order. This, together with the control of the altermagnetic order on nanoscale, was demonstrated experimentally. With these and other research highlights, described in more detail in the Scientific Report, the ALTERMAG team has made a significant progress towards all project’s objectives, namely Objective O1 aiming to establish the material basis of altermagnetism, Objective O2 aiming to unravel the unconventional spectroscopy of altermagnets, and Objectives O3 and O4 aiming to demonstrate altermagnetic spintronic functionalities and devices.
The anisotropic higher-partial-wave ordering in altermagnets bears physical analogies to the higher-partial-wave ordering in unconventional superfluidity and superconductivity discovered in the 1970s and 1980s. The founders of quantum mechanics have been asking questions about whether such unconventional phases can in principle exist since the 1940s. In superfluidity/superconductivity they were discovered a few decades later, while it took another several decades before the magnetic counterparts were eventually discovered by the PI and collaborators in the form of altermagnetism. Within two years preceding the ALTERMAG project, the PI and collaborators published predictions of the anomalous Hall effect and other spintronic phenomena in altermagnets. Between the submission and the starting date of ALTERMAG, two key works followed. The first one focused on a basic theoretical delineation and description of altermagnetism, and the second one on the broad potential of this unconventional magnetic phase in science and technology. During the first reporting period of the project, the experimental researched started from observations of the anomalous Hall effect. The ALTERMAG team then coordinated research which provided the decisive spectroscopic experimental evidence of altermagnetism. The discovery attracted extraordinary attention not only in the scientific community. Popular articles about altermagnets as a third distinct basic class of magnets were published, among others, in Science, Nature, ScienceNews, The Economist, Newsweek, or The Financial Times. Further spectroscopic evidence of altermagnetism was then provided by the PI and collaborators. In parallel, the prediction and observation of circular dichroism opened a direct way for microscopic imaging of the altermagnetic order. This, together with the control of the altermagnetic order on nanoscale, was demonstrated experimentally. With these and other research highlights, described in more detail in the Scientific Report, the ALTERMAG team has made a significant progress towards all project’s objectives, namely Objective O1 aiming to establish the material basis of altermagnetism, Objective O2 aiming to unravel the unconventional spectroscopy of altermagnets, and Objectives O3 and O4 aiming to demonstrate altermagnetic spintronic functionalities and devices.
The discovery of altermagnetism, led by the PI and collaborators, was listed among the 10 Breakthroughs of the year 2024 by Science:
M. Cantwell, The biggest science breakthroughs in 2024: From nitrogen-fixing organelles to a new form of magnetism, 2024 was full of scientific advances. Science 29 Jan 2025, https://www.science.org/content/article/biggest-science-breakthroughs-2024(opens in new window)
M. Cantwell, The biggest science breakthroughs in 2024: From nitrogen-fixing organelles to a new form of magnetism, 2024 was full of scientific advances. Science 29 Jan 2025, https://www.science.org/content/article/biggest-science-breakthroughs-2024(opens in new window)