Estimation of the charge carrier localization length from Gaussian fluctuations in the magneto-thermopower of La0.6Y0.1Ca0.3MnO3

Article

关键词: SHOWING GIANT MAGNETORESISTANCE;    COLOSSAL-MAGNETORESISTANCE;    THERMAL-CONDUCTIVITY;    THERMOELECTRIC-POWER;    SUPERCONDUCTIVITY;    LA1-XCAXMNO3;    TEMPERATURE;    MANGANITES;    BI2SR2CACU2O8;    TRANSITIONS;   

DOI  :  10.1103/PhysRevB.60.12322

来源: SCIE

【 摘 要 】

The magneto-thermoelectric power (TEP) Delta S(T,H) of perovskite-type manganese oxide La0.6Y0.1Ca0.3MnO3 is found to exhibit a sharp peak at some temperature T*=170 K. By approximating the true shape of the measured magneto-TEP in the vicinity of T* by a linear triangle of the form Delta S(T,H) similar or equal to S-p(H)+/-B+/-(H)(T* - T), we observe that B-(H)similar or equal to 2B(+)(H). We adopt the electron localization scenario and introduce a Ginzburg-Landau (GL)-type theory which incorporates the two concurrent phase transitions, viz., the paramagnetic-ferromagnetic transition at the Curie point T-C and the metal-insulator'' (M-I) transition at T-MI. The latter is characterized by the divergence of the field-dependent charge carrier localization length xi(T,H) at some characteristic field H-o. Calculating the average and fluctuation contributions to the total magnetization and the transport entropy related magneto-TEP Delta S(T,H) within the GL theory, we obtain a simple relationship between T* and the above two critical temperatures (T-C and T-MI). The observed slope ratio B-(H)/B+(H) is found to be governed by the competition between the electron-spin exchange JS and the induced magnetic energy MsHo. The comparison of our data with the model predictions produce T-C = 195 K, JS = 40 meV, M-o = 0.4M(s), and xi(o) = 5 Angstrom for the estimates of the Curie temperature, the exchange coupling constant, the critical magnetization, and the localization length, respectively. The magneto-TEP data obtained by other authors are discussed and Found to be consistent with the model predictions as well. [[S0163-1829(99)00734-1].

【 授权许可】

Free