Magnetic phase transitions pressure dependence

Magnetic phase transition temperatures and their pressure dependence in gadolinium... 

The activation volume, obtained from the pressure dependence of the reaction rate, has become a well-established, and often decisive, criterion for the determination of the reaction mechanism, so that variable-pressure NMR has also become an important tool in the understanding of chemical reactions. High gas pressures can be used to produce increased concentrations of a gas in solution, leading to faster reaction rates, advantageous shifts in chemical equilibria, or even entirely new chemical species. High-pressure NMR is an obvious technique for the study of such reactions. Nuclear magnetic resonance has also proven to be a powerful technique in solid-state physics, where variable-pressure experiments can be used to study phase transitions, transport phenomena, and electronic properties. 

Some properties show hysteresis, and these are not unique functions of the conditions (pressure, temperature) but depend also on the history or the way the state has been arrived at. Examples of such properties are the degree of magnetic or electric polarization in ferromagnetic or ferroelectric compounds at temperatures below the Curie temperature and phase transition such as melting or solidification. The transition temperature depends on whether it is approached from below or above the Curie temperature. The phase transitions in some ferroelectrics are described in Section 4.5. 

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