The influence of magnetic and structural heterogeneity on thermopower, magnetothermopower, electrical resistivity, and magnetoresistivity of NdSrMnO manganite.

The thermopower, S, magnetothermopower, Δ S/S, resistivity, ρ, and magnetoresistivity, Δρ/ρ, depending on the temperature T and magnetic field H, have been studied in an NdSrMnO single crystal consisting of three types of clusters: an antiferromagnetic CE-type with charge-orbital ordering (below the Neel temperature T ~ 145 K) and an A-type with T ~ 220 K; a ferromagnetic at 234 ≤ T ≤ 252 K, and a ferromagnetic metal phase below the Curie temperature T = 248 K. The thermopower was found to be negative, indicating the dominance of the electronic type of conductivity. In the S( T) curves, a sharp minimum is observed in the temperature range of 100 K ≤ T ≤ 133 K, close to T , where the absolute S value attains 53 μV/K. With a further increase in temperature, the absolute S value decreases rapidly; at 200 K it is equal to 7 μV/K. It then slightly increases, reaching its maximum value of 15 μV/K at a temperature of 254 K, which is close to T . The absolute thermopower decreased under the influence of the magnetic field; i.e., a negative magnetothermopower occurs. In {Δ S/S}( T) curves, a sharp minimum is observed at T = 130 K close to T , where the magnetothermopower reaches a huge value of ~45% at H = 13.23 kOe. A broad minimum in the {Δ S/S}( T) curves is observed near the Curie temperature and its value is also high, viz., ~15% in the maximum measuring magnetic field of 13.23 kOe. The extremely high magnetothermopower values mean that the charge-orbital ordered nanoclusters or ferron type make the main contribution to the thermopower of the entire sample. The behavior of the ρ( T) and {Δρ/ρ}( T) curves is similar to that of the S( T) and {Δ S/S}( T) dependencies, which is in agreement with this conclusion. [ABSTRACT FROM AUTHOR]