Magnetic and structural properties of FeCO3 at high pressures

Abstract

The structural and magnetic properties of siderite FeCO 3 have been studied by means of neutron powder diffraction at pressures up to 7.5 GPa and first-principles theoretical calculations. The lattice compression in the rhombohedral calcite-type structure is dominated by the reduction of the Fe-O bonds, while the changes of the C-O bonds are much less pronounced. The Néel temperature of the antiferromagnetic (AFM) ground state increases substantially under pressure with a coefficient dT N /dP = 1.8 K/GPa, which is about 1.5 times larger in comparison with those predicted by the empirical Bloch rule. The ab initio calculations were performed in the framework of the density functional theory including Hubbard-U correction. The calculated structural parameters and Néel temperature as functions of pressure provide a reasonable agreement with the experimental results. The analysis of the density of electronic states points toward increased covalent bonding between the Fe and O atoms upon pressure, giving rise to unexpectedly large pressure coefficient of the Néel temperature and reduced ordered magnetic moments of Fe atoms.

Magnetic and electronic properties of magnetite across the high pressure anomaly

“…6 ), may be explained by increased hybridization strength between the d -orbitals of Fe and p -orbitals of O atoms, leading to enhanced electronic delocalization 16 , 19 . Similar pressure-induced reduction of the ordered magnetic moment was recently also observed in the siderite FeCO 3 and underlying mechanism was evidenced by the ab-initio calculations 28 .…”

Effect of Doping on the Electronic Structure of the Earth’s Lower Mantle Compounds: FeXO3 with X = C, Al, Si

“…In the case of FeCO 3 and FeAlO 3 , the experimental values were obtained by neutron diffraction, and in the case of FeSiO 3 , the method of Mössbauer spectroscopy was used, together with a SQUID magnetometer. For FeCO 3 , the calculated magnetic moment of iron obtained in this work is closer to an experimental value than the previous calculation [ 47 ]. For FeAlO 3 , the magnetic moment of iron reported in [ 20 ] was calculated for another crystal structure, namely, a perovskite structure.…”

Fundamental insights into the stabilisation and chemical degradation of the corrosion product scales

“…In the regions around Fe ions in Fig. 3a, there are electrons overlaps to the adjacent oxygen, indicating the covalent contribution is seen between Fe and O atoms with the predominant of the ionic bond 27,29 .…”

“…Elizabeth et al 26 investigated the dolomite (CaMg(CO 3 ) 2 ) (1 0 4) phase and showed the Mg and Ca atoms have different bond distances with oxygen atoms and the main Ca-O interatomic distances turned to be greater after optimization of the surface. The analysis from Golosova et al 27 demonstrated that the anisotropic lattice compression of siderite was mainly contributed by the Fe-O bonds. Han et al 28 calculated the interactions of iron in Mg 1−x Fe x CO 3 from the iron-poor (x = 0.125) to the iron-rich (x = 1, FeCO 3 siderite) and found that the volume difference concerning MgCO 3 changes with Fe doping and resulted in the difference in relative enthalpy.…”