Figure 6: Schematic representation of equilibrium order degree versus temperature.
From: Inferred time- and temperature-dependent cation ordering in natural titanomagnetites
Dashed green line is equilibrium curve. (a) A rapidly cooled sample will follow the grey curve, departing from equilibrium at relatively high temperature (at the rate-dependent Tclose) and quenching in a low degree of order. A slowly cooled sample will follow the black curve, departing from equilibrium at a lower temperature and quenching in a higher degree of order. (b) During χ(T) measurements, a sample cooled slowly in nature may follow the red path on heating and the blue path on cooling, resulting in a large thermomagnetic irreversibility. If this same sample is then subjected to annealing in the lab at temperature Ta, it will rapidly follow the black dashed line to Ta, then slowly follow the solid black arrow during isothermal annealing. Upon quench, it will rapidly follow the black dashed line, ending at the solid black dot. If χ(T) is then measured on this same sample, the order degree would start at the black dot and follow a path towards the equilibrium curve. On cooling, it would again follow the blue dashed line.
