  The orthorhombic phase of Si-doped Fe carbide is synthesized at high
pressures and temperatures using laser-heated diamond anvil cell (LHDAC),
followed by its characterization using X-ray diffraction (XRD) measurements,
Transmission Electron Microscopy (TEM), and Raman spectroscopy. High-pressure
XRD measurements are carried out up to about 104 GPa at room temperature for
determination of the equation of state (EOS) parameters of the synthesized
sample. No evidence of structural transition is observed, though two anomalies
are found in the compression behaviour of our sample at about 28 and 78 GPa,
respectively. Pressure evolution of isothermal bulk modulus shows elastic
stiffening around 28 GPa followed by softening around 78 GPa. These anomalies
are possibly related to two different magnetic transitions driven by
pressure-induced anisotropic strain in the unit cell. Extrapolation of the
density profile of our study to the inner core conditions agrees very well with
PREM data with an uncertainty of about 3-4%. We have estimate bulk modulus
value seems to be 8-9% less than that of PREM data in the shown pressure range
and is best matched in comparison to other reported values for the non-magnetic
phase.
