ИСТИНА

We found that the thermopower of some doped manganites can be greatly enhanced by the existence of nanoclusters of the other crystalline and magnetic structure. Clusters make a larger contribution in thermopower than the main matrix. Increasing the number of nanoclusters, we can increase the thermopower. The researching of neutron and electron diffraction and magnetic properties of Sm0.5.5Sr0.45MnO3 have shown that there is a magnetic inhomogeneous state in it consisting of ferromagnetic (F) clusters with Curie point TC=134 K, A-type antiferromagnetic (AF) clusters with Neel temperature TNA~TC and CE-type AF clusters with TNCE=240 K. We have investigated the thermopower  and longitudinal magnetothermopower /=(αH-αH=0)/αH=0 of the monocrystalline and polycristalline Sm05.5Sr0.45MnO3 in magnetic field up to 13.2 kOe. Single crystal was annealed in oxygen which closes broken connection Mn-V-Mn (V is vacancy) and CE-type AF phase becomes dominant in the sample. In single crystal the broad maximum on the curves of temperature dependences α(T) includes TNCE, whereas the giant minimum on the {/}(T) curves is sharp and is located near the TNCE. Sharp decrease of α in TNCE under the action of magnetic field is connected with destruction of CE-type AF phase and with its charge order displacing oxygen ions. Electrical current, flowed in the sample at a α-measurement, causes Peltier effect on boundary of CE-type AF cluster and a temperature difference ∆T arises on this cluster. Internal thermopower, caused by influence of T, is equal to (1-2)T, where 1 is the thermopower of cluster and 2 is the one outside of its. In polycrystalline sample the broad maximum on the α(T) curves includes TC, and giant minimum on the {/}(T) curves in TC is sharp. Here the major contribution in α occurs from F clusters inside of which the crystalline lattice is compressed because of strong s-d exchange. Thereby magnetic inhomogeneity combined with strongly structural heterogeneity influences on thermopower and magnetothermopower in Sm0.55Sr0.45MnO3. The value of thermopower can be regulated by magnetic field. Thus, opens up new perspectives to the researching of similar big thermopower nanomaterials that can be used in environmentally friendly voltage generators.