Spontaneous Anomalous Hall Effect Arising from an Unconventional Compensated Magnetic Phase in a Semiconductor

The anomalous Hall effect, typically associated with metallic magnets, is conventionally linked to time-reversal symmetry breaking caused by either macroscopic magnetization in ferromagnets or noncollinear magnetic orders. In our research, we uncover a spontaneous anomalous Hall signal in epitaxial MnTe films, observed without any external magnetic field. Remarkably, MnTe is a semiconductor with collinear antiparallel Mn magnetic moments and no net magnetization. This unexpected Hall effect originates from the anisotropic crystal environment, where nonmagnetic Te atoms induce alternating spin polarization in the real-space crystal lattice and momentum-space electronic structure. This phenomenon is a hallmark of altermagnetism, a newly emerging magnetic phase.