2 research outputs found
Magnetic Ordering of Magnetite Inclusions in Olivine at Mantle Depths in Subduction Zones
Magnetite microinclusions
in metamorphic harzburgites,
derived
from the deserpentinization of the subducted hydrated oceanic lithospheric
mantle, were examined by synchrotron Mòˆssbauer spectroscopy
to investigate the chemical and magnetic environments of the Fe nuclei.
The data reveal a critical susceptibility of the octahedral sites
of the cubic structure of magnetite to chemical variations, which,
in turn, influences their magnetic properties in terms of hyperfine
magnetic field intensity and direction. Micromagnetites display substantial
remanent magnetization; however, the magnetic moment direction can
be significantly different among inclusions, even for those in close
spatial proximity. This evidence points to a kinetic control of the
composition of microcavities at mantle depths, implying that the use
of the remanent magnetic field of included magnetic phases to infer
large-scale implications on the Earth’s magnetic field requires
the development of complex geochemical and geodynamical models
Wet Chemical Synthesis and a Combined X-ray and Mòˆssbauer Study of the Formation of FeSb<sub>2</sub> Nanoparticles
Understanding how solids form is a challenging task, and few strategies allow for elucidation of reaction pathways that are useful for designing the synthesis of solids. Here, we report a powerful solution-mediated approach for formation of nanocrystals of the thermoelectrically promising FeSb<sub>2</sub> that uses activated metal nanoparticles as precursors. The small particle size of the reactants ensures minimum diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid–solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis. A time- and temperature-dependent study of formation of nanoparticular FeSb<sub>2</sub> by X-ray powder diffraction and iron-57 Mòˆssbauer spectroscopy showed the incipient formation of the binary phase in the temperature range of 200–250 °C