Suppression of magnetism under pressure in FeS: A DFT+DMFT study

A. V. Ushakov, A. O. Shorikov, V. I. Anisimov, N. V. Baranov, and S. V. Streltsov

Phys. Rev. B 95, 205116 – Published 11 May 2017

ABSTRACT

We investigate the evolution of the magnetic properties in FeS under pressure and show that these cannot be explained solely in terms of the spin-state transition from a high to low spin state due to an increase of the crystal field. Using a combination of density functional theory and dynamical mean-field theory (DFT+DMFT), our calculations show that at normal conditions the

{Fe}^{2 +}

ions are in the

3 d^{6}

high-spin (

S = 2

) state, with some admixture of a

3 d^{7} L - -

(

S = 3 / 2

) configuration, where

L - -

stands for the ligand hole. Suppressing the magnetic moment by uniform compression is related to a substantial increase in electron delocalization and occupation of several lower spin configurations. The electronic configuration of Fe ions cannot be characterized by a single ionic state, but only by a mixture of the

3 d^{7} L - -, 3 d^{8} {L - -}^{2}

, and

3 d^{9} {L - -}^{3}

configurations at pressures

\sim 7.5 GPa

. The local spin-spin correlation function shows well-defined local magnetic moment, corresponding to a large lifetime in the high spin state at normal conditions. Under pressure FeS demonstrates a transition to a mixed state with small lifetimes in each of the spin configurations.