Podrobnosti záznamu

Název
    Frequency-dependent susceptibility and other magnetic properties of Celtic and Mediaeval graphitic pottery from Bohemia: an introductory study
Autor
    Chlupacova, Marta
    Hrouda, František
    Laufek, Frantisek
    Nižňanský, Daniel
    Petakova, Zdenka
    Prochazka, Vaclav
Jazyk
    anglicky
Typ dokumentu
    článek v periodiku
Zdrojový dokument - seriál
    Studia Geophysica et Geodaetica
Svazek/č.
    Roč. 56, č. 3
Strany
    23
Rok
    2012
Výraz tezauru
    Celtic and Mediaeval graphitic pottery
    magnetic properties
    superparamagnetic particles
Klíčové slovo
    Bohemia
    Celtic
    Frequency-dependent
    Graphitic
    Introductory
    Magnetic
    Mediaeval
    Other
    Pottery
    Properties
    Study
    Susceptibility
Abstrakt (anglicky)
   Frequency-dependent magnetic susceptibility, its anisotropy (AMS), its temperature variation, natural remanent magnetization and time-dependent isothermal remanent magnetization as well as Mossbauer spectroscopy of a small collection of Celtic and Mediaeval graphitic pottery from Southern Bohemia were investigated. The mineral composition of the pottery is dominated by fragments of quartz, accompanied mainly by various silicates from granitoids and paragneisses, or by calcite, within the plastic component being probably illite but also graphite. No ferrimagnetic minerals were found in optical microscope, among Fe-oxides only limonite was observed, even though the bulk susceptibility of the pottery varies in the orders of 10(-4) to 10(-2) [SI]. This may indicate presence of ferromagnetic particles in the ultrafine (superparamagnetic, SP) state, which is confirmed by frequency-dependent susceptibility ranging from 3% to almost 16%. The low temperature susceptibility vs. temperature curve
   s are only moderately sloped, showing the Verwey transition only in one case. The high temperature curves mostly show presence of two magnetic phases, maghemite and magnetite. Cooling curves show distinctly lower susceptibilities than the heating curves indicating instability of the assemblage of ferrimagnetic minerals, particularly in temperatures slightly under 700 A degrees C. Mossbauer spectroscopy confirmed the results of the frequency-dependent susceptibility, showing the increase of ferrimagnetic sextets in the spectra measured at 4.2K, likely indicating maghemite as the distinct ferrimagnetic phase. The frequency-dependent AMS indicates preferred orientation of SP1,16 particles, coaxiality between SP1,16 grain AMS and whole specimen AMS indicate that all grains, ultrafine and coarser ones, were oriented by the same process, i.e. copying the pottery structure created during wheel-turning.
Přispěvatel
    UK Praha, Přírodovědecká fakulta
Kód přispěvatele
    UK, PřF
Zdrojový formát
    R
Datum importu
    27. 4. 2014