HR: 0800h
AN: MR31A-0130    [Abstracts]
TI: Acoustic Anomalies in Magnesioferrite up to 700 §C
AU: * Antao, S M
EM: sytle.antao@stonybrook.edu
AF: State University of New York @ Stony Brook, Mineral Physics Institute and Department of Geosciences, Stony Brook, NY 11794-2100 United States
AU: Jackson, I
EM: Ian.Jackson@anu.edu.au
AF: Australian National University, Earth Materials Research School of Earth Sciences, Canberra, ACT 0200 Australia
AU: Weston, L
EM: Lara.Weston@anu.edu.au
AF: Australian National University, Earth Materials Research School of Earth Sciences, Canberra, ACT 0200 Australia
AU: Kung, J
EM: jennifer.kung@stonybrok.edu
AF: State University of New York @ Stony Brook, Mineral Physics Institute and Department of Geosciences, Stony Brook, NY 11794-2100 United States
AU: Li, B
EM: Baosheng.Li@stonybrook.edu
AF: State University of New York @ Stony Brook, Mineral Physics Institute and Department of Geosciences, Stony Brook, NY 11794-2100 United States
AU: Chen, J
EM: Jiuhua.chen@stonybrook.edu
AF: State University of New York @ Stony Brook, Mineral Physics Institute and Department of Geosciences, Stony Brook, NY 11794-2100 United States
AU: Hassan, I
EM: ishmael.hassan@uwimona.edu.jm
AF: University of the West Indies, Department of Chemistry, Mona, KIN Kingston 7 Jamaica
AU: Liebermann, R C
EM: robert.liebermann@stonybrook.edu
AF: State University of New York @ Stony Brook, Mineral Physics Institute and Department of Geosciences, Stony Brook, NY 11794-2100 United States
AU: Parise, J
EM: john.parise@stonybrook.edu
AF: State University of New York @ Stony Brook, Mineral Physics Institute and Department of Geosciences, Stony Brook, NY 11794-2100 United States
AB: A recent study indicated that magnesioferrite spinel, MgFe₂O₄, displays two main transitions with increasing temperature: (1) a Curie transition at about 360°C (determined by thermal analyses, TA, in a magnetic field), and (2) relaxation of cations towards equilibrium at about 581°C as determined by Rietveld analysis (550 to 568°C observed by TA). Ultrasonic experiments were carried out at 300 MPa pressure in gas-medium high-pressure apparatus to determine if these two transitions have any effect on the acoustic properties of magnesioferrite. On heating, the travel times for both the P and S waves increase gradually up to 350°C. At 400°C there is an abrupt decrease in the travel times, which probably represents the Curie transition that was observed by TA at about 360°C. At 600°C, the S wave was unobserved, and the P wave showed a sharp increase in travel time up to 700°C. Beyond 700°C, the P-wave signal was very weak. The deterioration of signal quality and markedly greater travel times at the higher temperatures may reflect the onset of cation disorder or alternatively partial reduction of Fe³⁺ in the reducing environment of the mild steel jacket.
DE: 3999 General or miscellaneous
SC: Mineral and Rock Physics [MR]
MN: Fall Meeting 2005