3D-to-2D Evolution triggered paramagnetic-to-antiferromagnetic transformation

The dimensionality decrease from three-dimensional (3D) bulk to two-dimensional (2D) nanosheets was expected to made a significant influence on the physical-chemical properties of layered materials, which are of importance for materials design with enhanced functionalities. Here, in this work, we have demonstrated that a layered material, that has shown paramagnetic behavior at 3D bulk state, has displayed remarkable antiferromagnetic behavior with Neel temperature large to be about 140 K for the 2D nanosheets. This dramatical variation has been interpreted as the spin canting of the center metal ions as a result of enhancement in metal-to-ligand charge transfer between ligand and metal center, and d-d transition for metal ions, upon exfoliation. As a consequence, thermal and light irradiation-induced reversible spin-state switching, for both in colloidal suspension and at solid state, have been observed with 2D nanosheets. Compared with the performance enhancement in the literature, this kind of dimensionality decrease leading to subversive performance variations may open a new drive for creation of novel functions with nanomaterials.