ИСТИНА

We have investigated the thermopower a and longitudinal magnetothermopower a/a=(α_H-α_H=0)/α_H=0 of the monocrystalline and polycrystalline Sm05.5Sr0.45MnO3 in magnetic field up to 13.2 kOe. The broad maximum on temperature dependence of absolute value α(T) includes Tc, but near Tc is also the sharp giant minimum on the {delta a/a}(T) curves. Sharp decrease of α in Tc under the action of magnetic field is connected with destruction of the F nanoclusters in which the crystalline lattice is pressed by strong s-d exchange. Negative magnetothermopower in its minimum achieves the giant value of 90% in magnetic field H = 14,2 kOe. The changed crystalline lattice in these clusters excites the change of thermopower in them. This cluster’s thermopower influences on the voltage drop of whole sample during the measurement of thermopower and, consequently, on the effective value α of the whole sample. This means that F clusters make the basic contribution in the total thermopower.