Application of second order phase transition

1. Transition of a super conductor from super conducting to the normal state in zero magnetic field (It is a true second order transition).
2. Ferromagnetic to paramagnetic transition in a simple model.
3. Order-disorder transformation.

Lambda Transition

It is the third type of phase transition between the two liquid phases of He⁴, ordinary liquid helium l, and super fluid helium He ll***. This transition can occur at any point along the line separating these two liquid phases in Fig.2.13.

Fig. 2.13 Phase diagram of helium

From this figure, it is evident that He l and He ll can coexist in equilibrium over a range of temperature and pressures, and He l can be converted to He ll either by lowering the temperature, provided pressure is not too great, or by reducing the pressure, provided that the temperature is below 2.18 K.  A graph of C_p versus T for the two phases has the general shape shown in Fig.2.14, and the transition takes its name from the resemblance of the curve to the shape of the Greek letter λ. The value of C_p does not change discontinuously, but its variation with temperature is different in the two phases.

Fig. 2.14 Lambda transition