524 / 2019-03-19 20:57:24

Pressure-induced spin crossover of magnetic Mott-insulators: results of the hybrid functional

High-pressure; Spin crossover; First principles, Mott-insulator, Hybrid functional

全体主题 > High Pressure Physics and Materials Science

Under high-pressure, magnetic materials will undergo a spin crossover from the high-spin (HS) state to the intermediate-spin (IS) state or to the low-spin (LS) state. The spin crossover has significant effect on the material’s properties, such as volume reduction and insulator-metal transition. Pressure-induced spin crossover in the magnetic Mott-insulators are important subjects in both high-pressure physics and condensed matter physics, since it is important to understanding the physics of Mott-insulators such as (FeO and SrCoO3). Furthermore, related research can help us to clarify the properties of the Earth’s low-mantle minerals, since Fe-bearing MgO and FeAl-bearing MgSiO3 has spin-polarized Fe-O bond, a famous strongly correlated system.
Since the magnetic Mott-insulators are strongly correlated material, the LDA+U method is generally used to simulate their properties. To determine the effective U values, bandgap and lattice constants at the ambient pressure are usually used as the criterion. In some cases, the effective U values at the ambient pressure are used to simulate the behaviors of pressure-induced spin crossover. However, the simulated properties, e.g., spin crossover pressures, cannot reproduce the experimental observations, which are mainly due to the application of the same U values on all the configurations under different pressures and different spin states.
In this talk, we will present our results about the spin crossover of Fe-bearing MgO and transition-metal phosphorus trichalcogenide by using the hybrid functional. Our result show that the spin crossover behaviors of the magnetic Mott-insulators can be well described. Furthermore, the effects of Fe distributions on the spin crossover of Fe-bearing MgO will also be presented.