Ultrathin 2-D van der Waals (vdW) semiconductor materials have procured scientific and technological interest since the discovery of single layered graphene in 2004.¹ Similar to graphene, transition metal trichalcogenides, with the general chemical formula MPX₃ (M= 1st row transition metals, X = chalcogenides), possess fast electron transport and strong spin orbit coupling without the drawback of no bandgap. These vdW inorganic lamellar compounds are characterized by strong intralayer covalent bonding and weak vdW interaction between adjacent layers. Furthermore, they possess weak vdW interlayer interactions meaning that cleaving few- or single-layers from the bulk material is relatively simple using either mechanical or liquid exfoliation techniques. Furthermore, the transition metal atoms endow these materials with magnetic (either ferromagnetic or antiferromagnetic) and magneto-optical properties which can be utilized for new generation 2-D magnets and opto-spintronic devices. Yet, the fundamental understanding of these materials as well as the manipulation of their intrinsic magnetism via external stimuli remains to be an unexplored endeavor.

MPX₃ offers a large range of chemical compositions tunable via the M and X elements, consequently forming semiconductors with varying band gap energies ranging from UV to near- infrared. In this way the intrinsic magnetic properties that originate from the M atoms in the MPX₃ materials can also be tuned. Depending on the M atoms within the MPX₃ layers, they can be endowed with magnetic (either ferromagnetic or antiferromagnetic) and magneto-optical properties. In the case of FePS₃ antiferromagnetic Ising magnetic ordering is exhibited. Investigations of bulk and few layer FePS₃ have shown optical linear dichroism believed to be attributed to its zigzag antiferromagnetic ordering and anisotropic crystal structure. However, the intrinsic magnetic properties of FePS₃ and their effect on the material’s linear dichroism has yet to be explored. Furthermore, the anisotropic crystal structure of FePS₃ gives rise to inequivalent K(K’) points in the brilloiun zone. This suggests the possibility of valleytronic properties as seen in transition metal dichalcogenides (TMDs).^2–4 To date, these properties have not being shown in TMTCs such as FePS_3.    

In this talk, evidence of optical linear dichroism will be shown as a function of external magnetic field and temperature. Furthermore, the possibility of valleytronic properties of FePS₃ will be shown using circularly polarized excitation as a function of external magnetic field.