  Recent developments have introduced a groundbreaking form of collinear
magnetism known as "altermagnetism". This emerging magnetic phase is
characterized by robust time-reversal symmetry breaking, antiparallel magnetic
order, and alternating spin-splitting band structures, yet it exhibits
vanishing net magnetization constrained by symmetry. Altermagnetism uniquely
integrates traits previously considered mutually exclusive to conventional
collinear ferromagnetism and antiferromagnetism, thereby facilitating phenomena
and functionalities previously not achievable within these traditional
categories of magnetism. Initially proposed theoretically, the existence of the
altermagnetic phase has since been corroborated by a range of experimental
studies, which have confirmed its unique properties and potential for
applications. This review explores the rapidly expanding research on
altermagnets, emphasizing the novel physical phenomena they manifest,
methodologies for inducing altermagnetism, and promising altermagnetic
materials. The goal of this review is to furnish readers with a comprehensive
overview of altermagnetism and to inspire further innovative studies on
altermagnetic materials which could potentially revolutionize applications in
technology and materials science.
