Determination and significance of the Mn(II) Zero-Field Splitting (ZFS) interaction in the geochemistry of travertines

A new approach to marine fish otoliths study: electron paramagnetic resonance

“…The value of this parameter (22.4 mT) is consistent with the values described in the literature for aragonite biomineral (shells), 12.53–25.0 mT, (White et al , 1977; Raju et al , 2002) and aragonite synthetic and mineral, 23.2–25.0 mT (Angus et al , 1979; Slezak et al , 1979). However, these values are higher than those obtained in calcites, 8.1–10.6 mT (Angus et al , 1979; Montegrossi et al , 2006; Vongsavat et al , 2006; Angiolillo & Graneto, 2008), because the incorporation of Mn 2+ in aragonite is related to a greater distortion of the axial site of Ca 2+ , resulting in lower symmetry of this site and causing the split of each line of the sextet of Mn 2+ into three (Angus et al , 1979).…”

“…The ZFS causes a splitting of the electronic energy states even in the absence of an external magnetic field. This effect can be observed as the distortion of the lines of the Mn 2+ sextet, especially in the last line (higher magnetic field), which can be used to obtain the ZFS parameter D, as proposed by Montegrossi et al (2006). This distortion is indicated in Figure 2 by distance (in miliTesla) of the two dotted vertical lines, and shows that all specimens have the same parameter D, estimated in 22.4 mT.…”

“…The structure of the EPR spectrum of Mn 2+ is related to the chemical and physical properties of CaCO 3 , indicating EPR as a potential technique for probing the crystallization conditions (Montegrossi et al , 2006). In polymorphs of CaCO 3 , the Mn 2+ is coordinated by oxygen atoms.…”

Biotic and inorganic control on travertine deposition at Bullicame 3 spring (Viterbo, Italy): A multidisciplinary approach

“…carbonate/bicarbonate availability, pH) on the bacterial activity. Montegrossi et al (2006), in a study on some Italian travertine deposits, revealed an unusual variability of the zero-field splitting parameter by Electron Paramagnetic Resonance (EPR) spectroscopy, suggesting that chemical ordering of cations in travertine can be investigated, as already proposed in the pioneering study by Kretz (1982). Calcite is known, in fact, to retain many non-equilibrium depositional features (e.g.…”

“…Relations(1)and(2)are defined for D, W D , D 6 , W 6 values expressed in Tesla (1T = 10000 G), according toMontegrossi et al (2006).…”