Probing magnetic phase diagrams of two-dimensional antiferromagnets


Two-dimensional (2D) magnets decouple from the substrates, allow electrical control, and are mechanically flexible, making them integratable into emergent heterostructures for advanced properties and applications previously impossible. Among them, antiferromagnets hold promise for high-speed, low-power spintronics because they have magnetic resonance frequencies in the terahertz regime, null stray field for vanishing cross-talk between adjacent bits, and robustness against the external magnetic field perturbation. However, there is no good way to probe the magnetic states of the antiferromagnets in the 2D limit, due to their atomic thickness and net vanishing magnetization. In this talk, by means of electrical transport and optical spectroscopy measurements under low temperature and high magnetic field, I will give a few examples to study the magnetic evolution processes of 2D antiferromagnetic materials down to monolayer limit. For example, we detected the subtle phase transition behavior of exfoliated stripy antiferromagnet CrOCl under varying temperature and magnetic field and clarified its controversial spin structure, multiple degrees of freedom coupling of CrOCl under the 2D limit, and unraveled the odd-even layer-number effect and layer-dependent magnetic phase diagrams in A-type anitferromagnet MnBi2Te4.