Above the critical temperature there is only a single fluid phase no matter what the applied pressure.

They have to stay cooled down below their critical temperature.

As indicated, this is largely due to the very low critical temperature at which these materials become magnetic.

Above the critical temperature and pressure, a substance has only a single fluid phase.

Vortices are able to form above this critical temperature, but not below.

Thus, above the critical temperature a gas cannot be liquefied by pressure.

The point P represents the gas at its critical temperature, pressure and volume.

Figure 3.11 shows two isotherms below the critical temperature of C02.

(ii) What do you understand by the terms real gas and critical temperature?

It is also where the critical temperature and critical pressure meet.