Pressure-induced spin transitions in 2D materials

Figure caption: Spin cross overs induced by pressure, determined by X-ray Emission Spectroscopy at HPCAT.
Figure caption: Spin cross overs induced by pressure, determined by X-ray Emission Spectroscopy at HPCAT.

Spin cross over may be induced by external stimuli such as light, heat, pressure, and magnetic fields, and provides an electronic origin responsible for corporative structural, electrical, magnetic, and/or optical alterations, with wide applications such as in memory, display, and sensor technologies. Based on recent experiments at HPCAT, together with electronic transport data, a research group observed a pressure-driven spin-cross-overs in the 2D honeycomb antiferromagnetic materials MnPS3 and MnPSe3 at room temperature. Applying pressure to the confined 2D systems leads to a dramatic magnetic moment collapse of Mn2+ (d5) from S = 5/2 to S = 1/2. Significantly, a number of collective phenomena were observed along with the spin change, including a large lattice collapse (∼20% in volume), and the formation of metallic bonding. Experimental evidence shows that all of these events occur in the honeycomb lattice, indicating a strongly cooperative mechanism that facilitates the occurrence of the abrupt pressure-driven spin transition. This result not only provides a new mechanism for novel switching materials that are applicable for sensor and memory devices, but also offers a platform to study the fundamental relationship between spin, orbital, lattice, and macroscopic functionalities under pressure. More in Y. Wang, et al., JACS, 138, 15751, 2016.