Competition between the double exchange and charge ordering interactions in the bandwidth controlled ðLa;NdÞ0:8Na0:2MnO3 manganites
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چکیده
Structural, magnetic, and transport properties of ðLa1 xNdxÞ0:8Na0:2MnO3 ð0pxp1Þ are studied. The system exhibits a rhombohedrally distorted perovskite structure for xp0:2 and it converts to an orthorhombic structure for xX0:4: Re-entrant ferromagnetic-type charge ordering transitions are observed in the narrow bandwidth samples ðxX0:8Þ: For T > 77 K; the compounds show metal to insulator transitions except Nd0:8Na0:2MnO3: The transition temperatures are equal to the corresponding Curie temperatures. Combining our results with the published data on manganites doped with divalent alkali earth cations, we propose that the double exchange interaction in ðLa1 xNdxÞ0:8Na0:2MnO3 is stronger than that of the divalent cations doped manganites with the same average Asite radius and hole concentrations. The resistivity data above the metal to insulator transition temperature for the charge ordered sample are discussed in the frame work of the variable-range hopping model. r 2004 Elsevier B.V. All rights reserved. PACS: 75.47.Lx; 75.47.Gk; 75.30.Kz
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تاریخ انتشار 2004