Two-dimensional magnetism in a van der Waals semiconductor

Since the recent discovery of ferromagnetism in exfoliated flakes of CrI₃ and Cr₂Ge₂Te₆, interest in two-dimensional (2D) ferromagnetic systems has increased. Previously predicted to be prohibited by thermal fluctuations, the existence of 2D magnetically ordered systems offers an ideal platform for examining novel quantum phenomena and opens up opportunities for emerging applications, including magneto-optic and magneto-electronic devices, spintronics, and quantum computing. For use in applications, there is a crucial need to develop 2D materials that simultaneously exhibit ferromagnetism and semiconducting behaviors. Towards this end, we recently synthesized an air stable van der Waals magnetic semiconductor. 2D sheets can be prepared through mechanical exfoliation for measurement and incorporation into more complex heterostructures. Using electrical transport, second harmonic generation spectroscopy, photoluminescence spectroscopy, and scanning tunneling spectroscopy, we investigate the electrical and magnetic properties of this material in the 2D limit. We present clear evidence of layered antiferromagnetic ordering at ~130K, below which the spins in each sheet are aligned ferromagnetically parallel to the plane while the interlayer coupling is antiferromagnetic.