Orbital phase transition in Pr$_{1-x}$Ca$_x$MnO$_3$

The phenomenological theory of phase transition in Pr$_{0.6}$Ca$_{0.4}$MnO$_{3}$ manganite is developed. It is shown that this is the orbital phase transition and that the two electronic states of the manganese ion, which are discussed in the literature, result from two different types of condensation of the same orbital order parameter. Thus, the manganese ions in Pr$_{1-x}$Ca$_x$MnO$_3$ manganites with $0.3\leq x\leq 0.5$ may be in either of the two electronic states, depending on the thermodynamic parameters.