Tunneling Conductivity of Manganites with Negative Magnetoresistance

Tunneling investigations of ferromagnetic La$\text{}_{0.6}$Sr$\text{}_{0.4}$MnO$\text{}_{3}$ ceramic samples showing negative magnetoresistance effect were carried out in two types of junctions: symmetric "break junctions" and asymmetric ceramics-insulator-metal junctions. The results are consistent with the presence of small ferromagnetic clusters in the insulating barriers of both types of junctions and suggest a two-phase state realized by impurity mechanism of phase separation.