Ultrathin nanosheets of CrSiTe₃: A semiconducting two-dimensional ferromagnetic material

Finite range ferromagnetism and antiferromagnetism in two-dimensional (2D) systems within an isotropic Heisenberg model at non-zero temperature were originally proposed to be impossible. However, recent theoretical studies using an Ising model have shown that 2D magnetic crystals can exhibit magnetism. Experimental verification of existing 2D magnetic crystals in this system has remained exploratory. In this work we exfoliated CrSiTe₃, a bulk ferromagnetic semiconductor, to mono- and few-layer 2D crystals onto a Si/SiO₂ substrate. Raman spectra indicate good stability and high quality of the exfoliated flakes, consistent with the computed phonon spectra of 2D CrSiTe₃, giving strong evidence for the existence of 2D CrSiTe₃ crystals. When the thickness of the CrSiTe₃ crystals is reduced to a few layers, we observed a clear change in resistivity at 80-120 K, consistent with theoretical calculations of the Curie temperature (T_c) of ∼80 K for the magnetic ordering of 2D CrSiTe₃ crystals. The ferromagnetic mono- and few-layer 2D CrSiTe₃ indicated here should enable numerous applications in nano-spintronics.