Diapositive 1

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A new three-axis vibrating sample magnetometer
for continuous high-temperaturemagnetization
measurements Applications to paleo- and
archeointensity determinations
Maxime LE GOFF and Yves GALLET
EPSL, 2004, 229/1-2 pp. 31-43.
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• Paleo- and archeointensity studiesare fastidious
  and often unproductive
• due to poor data quality

It is possible to make them fasterby measuring
the magnetizationat high temperatures
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TRIAXE SENSOR
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High-temperature version of the Thellier and
Thellier method revised by Coe

• must take into account the thermal dependence of
  the spontaneous magnetization

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High-Temperature Magnetization Measurements
Heating Troom to T1 (H0)
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High-Temperature Magnetization Measurements
Heating T1 to T2 (H0)
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High-Temperature Magnetization Measurements
Cooling to T1 andHeating T1 to T2 (H0)
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High-Temperature Magnetization Measurements
Applying Hlab 70µT
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High-Temperature Magnetization Measurements
Cooling T2 to T1 (H 70µT)
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High-Temperature Magnetization Measurements
Hlab 0µT
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High-Temperature Magnetization Measurements
Heating T1 to T2 (H0)
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Two possibilities to derive intensity data
TRM
NRM
Remaining NRM (?1) and TRM (?5) fractions
between Ti and T2 ? R ratio
Lost NRM (?1) and TRM (?5) fractions between
T1 and Ti ? R ratio
R(Ti) Hlab ?1(Ti) / ?5(Ti) R(Ti) Hlab
?1(Ti) / ?5(Ti)
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Test on a pseudo NRM acquired in a field of 50µT
in the same conditions as the laboratory TRM
(Hlab50 µT)
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Ancient NRM R increasing, R much more constant
R, R (µT)
Ti, (C)
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Cooling rate effect
R must be considered
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Correction for the TRM anisotropy
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Comparison between archeointensity data obtained
from the Thellier and Thellier method revised by
Coe and from the Triaxe
(Samples from Mesopotamia previously studied by
Genevey et al., JGR, 2003)
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Selection criteria

• A large NRM fraction must be involved
• Expected behaviour of R and R curves

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Example of rejected sample
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Archeointensity results from a site of baked
bricks from Mesopotamia (Mari, Syria)
6 samples
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Comparison between archeointensity results
obtained from the Thellier and Thellier and
Triaxe methods
H (µT)
Age (BC)
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CONCLUSIONS

• The experimental procedure was successfully
  tested with archeological baked materials.? We
  need now to work on volcanic samples.
• Other applications of the Triaxe - Viscosity
  at high temperature.- Alteration.- Coupling
  between different magnetic phases.- etc.

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Remaining NRM (1) and TRM (5) between Ti and T2
? R ratio
Lost NRM (1) and TRM (5) between T1 and Ti ? R
ratio
R(Ti) Hlab ?1(Ti) / ?5(Ti) R(Ti) Hlab
?1(Ti) / ?5(Ti)
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High-Temperature Magnetization Measurements
Cooling T2 to T1 (H0)