TheJ(eff)=1/2 Antiferromagnet Sr2IrO4: A Golden Avenue toward New Physics and Functions

Iridates have been providing a fertile ground for studying emergent phases of matter that arise from the delicate interplay of various fundamental interactions with approximate energy scale. Among these highly focused quantum materials, the perovskite Sr2IrO4, which belongs to the Ruddlesden-Popper series, stands out and has been intensively addressed in the last decade, since it hosts a novelJ(eff)= 1/2 state that is a profound manifestation of strong spin-orbit coupling. Moreover, theJ(eff)= 1/2 state represents a rare example of iridates that is better understood both theoretically and experimentally. Here, Sr(2)IrO(4)is taken as an example to review the recent advances of theJ(eff)= 1/2 state in two aspects: materials fundamentals and functionality potentials. In the fundamentals part, the basic issues for the layered canted antiferromagnetic order of theJ(eff)= 1/2 magnetic moments in Sr(2)IrO(4)are illustrated, and then the progress of the antiferromagnetic order modulation through diverse routes is highlighted. Subsequently, for the functionality potentials, fascinating properties such as atomic-scale giant magnetoresistance, anisotropic magnetoresistance, and nonvolatile memory, are addressed. To conclude, prospective remarks and an outlook are given.