Giant Magnetothermopower in Sm0.55Sr0.45MnO3 Manganite

Thermopower α and magnetothermopower ∆α/α were studied in the Sm0.55Sr0.45MnO3 samples, containing clusters of three types: ferromagnetic clusters with the Curie temperature TC = 126 K, A-type antiferromagnetic clusters with the Neel temperature TNA ≥ TC and CE-type antiferromagnetic clusters with the TNCE = 240 K. The curves of temperature dependence of α (T) have a large maximum including TC and TNCE and the sharp minimum on the {∆α/α}(T) curves in the TC-region. Negative magnetothermopower in minimum achieves the giant value ~ 85% in magnetic field 14.17 kOe. It is shown that thermopower is largely caused by the presence of ferromagnetic nanoclusters of ferron-type and to a lesser degree of CE-type antiferromagnetic clusters, in which there is a charge ordering, displacing oxygen ions.