Fundamentals and applications of altermagnetism

Altermagnetism has recently emerged as a new class of collinear magnetic order that transcends the conventional dichotomy between ferromagnetism and antiferromagnetism. Although altermagnets exhibit zero net magnetization in real space, they possess momentum-dependent spin splitting arising from their unique crystal symmetry, enabling phenomena that combine key advantages of both magnetic orders. These include large spin splitting without spin–orbit coupling, anomalous transport responses associated with broken time-reversal symmetry, and efficient magnetic-domain control, making altermagnets a promising platform for next-generation spintronic devices. Rapid progress in symmetry-based theory, material discovery, and experimental characterization has substantially advanced our understanding of this emerging magnetic phase. In this review, we summarize the fundamental concepts of altermagnetism, including its symmetry principles and magnetic multipole description, and discuss recent experimental developments based on transport, angle-resolved photoemission spectroscopy, magneto-optical, nonlinear optical, and terahertz spectroscopies. We further highlight recent advances in spintronic applications, domain manipulation, and future research directions, providing a comprehensive overview of the current status and prospects of altermagnetic materials.