4.7 Article

Magnetoresistance, magnetothermopower, magnetothermal conductivity and magnetostriction in La1-xNaxMnO3 (0 ≤ x ≤ 0.05)

期刊

CERAMICS INTERNATIONAL
卷 47, 期 1, 页码 393-399

出版社

ELSEVIER SCI LTD
DOI: 10.1016/j.ceramint.2020.08.145

关键词

Na doped LaMnO3; Magnetic properties; Thermal conductivity; Thermal expansion

资金

  1. Ministry of Education, Singapore [R144-000-404-114]

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This study investigates the impact of magnetic field on electrical and thermal properties of La1-xNaxMnO3 series. It was found that at the onset of ferromagnetic spin ordering, resistivity and thermopower exhibit peaks while thermal conductivity shows a sudden increase. External magnetic field influences thermal properties and thermal expansion mostly around the Curie temperature, while its effect on resistivity extends to as low as 10 K.
We report the influence of the magnetic field on electrical resistivity (rho), thermal conductivity (kappa), thermopower (S), and linear thermal expansion (Delta L/L-0) in La1-xNaxMnO3 series (x = 0, 0.01, 0.02, and 0.05) over a wide range of temperature. While LaMnO3 is an antiferromagnetic insulator, the doping with Na weakens the inter-planner antiferromagnetic coupling and transforms it into a ferromagnetic metal by promoting the double exchange coupling between Mn3+ and Mn4+ ions. rho and S show peaks, whereas, kappa shows a sudden increase at the onset of ferromagnetic spin ordering in the samples. Dominant charge carriers are holes in these doped compounds as indicated by the positive sign of S. High-temperature transport is explained in the context of the small polaron hopping model. External magnetic field influences thermal properties (S and kappa), and Delta L/L-0 mostly around the Curie temperature (TC), while it affects rho to as low as 10 K. Enhancement of kappa at the insulator-metal transition, on the application of external magnetic field, suggests a decrease in spin-wave scattering. The highest value of negative magnetoresistance (similar to 69.7%) and negative magnetothermopower (similar to 80.4%) is obtained for x = 0.02 and the value decreases for higher dopant concentration.

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