Thermoremanence magnetization field dependence

Fig. 66. The temperature dependence of the thermoremanent magnetization along the c-axis of LuFe O., for several values of the cooling field. (lida 1988.)...

Fig. 67. The temperature dependence of the saturation magnetization (open circles and a broken line) and the thermoremanent magnetization (solid lines) along the c-axis of LuFe204. The latter is induced by cooling from 250 K down to 4.2 K in an external magnetic field of 140 kOe and measured without field by successive heating-cooling cycles with increasing T, the maximum temperature of the cycle, (lida et al. 1987.)...

The difference of the thermoremanent magnetization (fig. 65) or the coercive field (fig. 64), due to the rare earth element, is attributed to the difference in the size of the domain or the coherence length of the spin ordering. That is consistent with a narrower Mossbauer absorption in LuFe20 than in non-stoichiometric YFCjO at low temperatures. This dependence on the rare earths should be correlated to the difference of electronic properties described in the last section. 

If the microscopic dwell times are all much larger than the measurement time, then one probes the system as a static distribution of its parameters in order to deduce the state in which the system was prepared, by its previous temperature, applied field, and structuro-chemical history. For example, this would correspond to a remanence magnetization measurement, in the absence of time or relaxation effects. Alternatively, one can consider that all the particles in the sample that have microscopic dwell times much larger than the measurement time form a subgroup or subsystem that has reliably preserved a subsystem-specific remanence signal. Since dwell times are highly temperature dependent (Eqn. 2), partial thermoremanence measurements are a powerful tool to reconstruct a rock s thermomagnetic history. 

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