The massive resurgence of interest for manganites thin films is connected with hope for applying these materials in commercial devices. The goal of this work is to establish the influence of temperature, applied magnetic field, current and time on the most industry-important property - resistivity.

In this paper we present the influence of manganese doping on thin manganite films properties. The measurements were carried out on 100 nm thin films family (La_0.7Ca_0.3)_1-xMn_1+xO₃, x=0, 0.1 and 0.2. The samples were deposited onto LaSrGaO₄ substrates using PLD method. All films are single-phase, oriented along the pseudo-cubic axis [100] and have the same structural symmetry.

Three types of experiments were conducted. In the first one R(T) curves were registered for five magnetic field and four current values (B=0, 0.1, 1, 4, 7T and I=10nA, 0.1µA, 1µA, 10µA). The shift of T_c, as well as, the resistivity changes are observed. In the (La_0.7Ca_0.3)_0.8Mn_1.2O₃ sample, the CMR reaches the value of ~80% and a resistivity switching in low field, e.g., 0.2T, is observed. This switching occurs only at low I values, e.g., 10nA, and may be connected with percolative conduction. The time and history characteristics are also done. Thus, in the above sample an emergence of a new, in comparison with the x=0 composition, insulating and metastable ground state has been identified. According to the Mott's model, carriers in this insulating state are highly correlated. To prove it, the resistivity magnetic loops R(B) were studied. The hysteresis occurs at low temperatures, where the ground state changes. The I-V characteristics were also measured. Their evolution before and after applying magnetic field at several temperatures is observed. The current induced phenomena and their discussion will be presented.