Evidence for a pressure-induced spin transition in olivine-type LiFePO4 triphylite

Abstract

We present a combination of first-principles and experimental results regarding the structural and magnetic properties of olivine-type LiFePO 4 under pressure. Our investigations indicate that the starting P bnm phase of LiFePO 4 persists up to 70 GPa. Further compression leads to an isostructural transition in the pressure range of 70-75 GPa, inconsistent with a former theoretical study. Considering our first-principles prediction for a high-spin to low-spin transition of Fe 2+ close to 72 GPa, we attribute the experimentally observed isostructural transition to a change in the spin state of Fe 2+ in LiFePO 4 . Compared to relevant Fe-bearing minerals, LiFePO 4 exhibits the largest onset pressure for a pressure-induced spin state transition.

Magnetic Properties of Multifunctional 7LiFePO4 under Hydrostatic Pressure

“…An early high pressure XRD investigation reported a structural transition to a space group Cmcm at a critical pressure below 65 kbar (34). However, other studies (35) indicate a much higher critical pressure. Further, theoretical calculations based on the Cmcm structure predict a decrease in the ordered Fe magnetic moment (36) with applied pressure, as shown in Fig.…”