Influence of the magnetic and structural neterogeneities on the thermopower, magnetothermopower, and spontaneous generation of an electric voltage in the manganite Sm0.55Sr0.45MnO3статья
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Дата последнего поиска статьи во внешних источниках: 2 сентября 2014 г.
Аннотация:The thermopower alfa and magnetothermopower delta alfa/alfa have been studied on on single-crystal Sm0.55Sr0.45MnO3 samples consisting of three types of magnetic clusters (ferromagnetic clustes with the Curie temperature T_C = 134 K, the A-type antiferromagnetic clusters with Neel temperture T_NA >= T_C and the CE-type antiferromagnetic clusters with T_NCE = 240 K). The temperature dependences of alfa and delta alfa/alfa have extremes in the vicinity of T_NCE, namely, a wide maximum in curve alfa(T) and a sharp minimum in curve {delta alfa/alfa}(T). The negative magnetothermopower in the minimum has a giant value of 50% in the magnetic field 13.2 kOe. The thermopower is shown to be mainly due to the existence of the CE-type antiferromagnetic clusters, in which there is the charge-orbital (CO) ordering displaced the oxygen atoms. The changed crystal lattice inside these clusters changes the value of the thermopower inside them. This thermopower influences the voltage drop on the sample during measuring the thermopower and, thus,the effective value of alfa of the whole sample. The applying a magnetic field near T_NCE accelerating the destruction of the CE-type antiferromagnetic order causes the sharp decrease in the thermopower of the whole sample. It implies that the CE-type CE-type antiferromagnetic clusters with the CO ordering make main contribution to the thermopower of the whole sample.