Other
Scientific paper
Feb 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995jgr...100.3285v&link_type=abstract
Journal of Geophysical Research (ISSN 0148-0227), vol. 100, no. E2, p. 3285-3295
Other
2
Chemical Properties, Hematite, Hydroxides, Manganese, Mars Surface, Precipitation (Chemistry), Reflectance, Antiferromagnetism, Magnetization, Spectrum Analysis, Synthesis (Chemistry)
Scientific paper
Goethite-bearing samples with values of Mn(s) (Mn/(Mn+Fe) mole fraction) up to 0.206 were synthesized by precipitation from alkaline solution. Samples with Mn(s) less than or equal 0.061 were single-phase Mn-goethites: samples with higher Mn(s) values contained another Mn-bearing phase (probably jacobsite). Mn-hematites were prepared by dehydroxylation of corresponding Mn-goethites at 500 C. Orthorhombic a and b unit cell dimensions of Mn-goethites changed in a linear manner with Mn(s), but not at rates predicted by the Vegrad law. Hexagonal unit cell dimensions of Mn-hematites did not vary with Mn(s). Moessbauer parameters isomer shift (IS), quadrupole splitting (QS), and hyperfine field (Bhf) were measured at 293 and 15 K. For all single-phase Mn-goethites and Mn-hematites (Mn(s) less than or equal 0.061), magnetic splitting was observed at both temperatures. At 293 K, small but systematic decreases in Bhf were observed with increasing Mn substitution; IS and QS were not dependent on Mn(s). Mn substitution strongly lowered the Morin transition temperature of hematite. At 15 K, the Morin transition was not present for Mn(s) greater than 0.020(4). The saturation magnetization of Mn-goethites and Mn-hematites (Mn(s) less than or equal 0.061) was the expected zero (within error) for antiferromagnetic goethite and for hematites obtained from dehydroxylation of goethites. Mn-geothites with Mn(s) greater than 0.061 were magnetic because of the presence of strongly magnetic jacobsite. For reflectivity spectra, bands resulting from MN(3+) were centered near 454 and 596 nm for Mn-goethites and near 545 and 700 nm for Mn-hematites. There is evidence for a approximately 700 nm band in spectral data for Martian bright regions, but association of it with Mn(3+) is not a unique interpretation. Comparison of laboratory and Martian spectral data implies that Mn(s) less than 0.032 for the Mn(3+) content of Martian hematites.
Helmke Philip A.
Lauer Howard V. Jr.
Morris Richard V.
Vempati R. K.
No associations
LandOfFree
Reflectivity and other physicochemical properties of Mn-substituted goethites and hematites does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Reflectivity and other physicochemical properties of Mn-substituted goethites and hematites, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Reflectivity and other physicochemical properties of Mn-substituted goethites and hematites will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1635379