Critical scaling and percolation in manganite films

In this work the critical behaviour of films of La_0.7Ba_0.3MnO₃, La_0.7Sr_0.3MnO₃, La_0.7Ca_0.3MnO₃ and (LaMn)_1-δO₃ is studied. Apart from the La_0.7Ca_0.3MnO₃ film, each of these manganite films shows a continuous phase transition with mean-field critical exponents. The analysis of the critical amplitudes indicates the formation of spin polarons. The zero-field resistivity of the La_0.7Ca_0.3MnO₃ film is consistent with a model of percolative phase separation.