Comment on 鈥楽tructural properties and electrical resistivity of Na-substituted lanthanum manganites: La_{1鈭?span style='font-style: italic'>x}Na_xMnO_3+y (x = 0.1, 0.125 and 0.15)鈥?and 鈥楽tructure and electrica

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• 作者：E. Rozenberg ; ^{evgenyr@bgu.ac.il}
• 关键词：Oxide materials ; Structural properties ; Electronic transport ; Grain boundary effects
• 刊名：Journal of Alloys and Compounds
• 出版年：2012
• 期刊代码：45_09258388
• 类别：ms
• 出版时间：25 August, 2012
• 卷：533
• 期：Complete
• 页码：41-42
• 文件大小：145 K

摘要

In the recent papers (Varshney et al. and Mansuri et al. ) the authors reported data on structure and electrical transport, i.e., resistivity (蟻) versus temperature (T) and magnetic field (H) on polycrystalline manganite systems La_1鈭?em>xNa_xMnO_3+y and La_1鈭?em>xBa_xMnO₃. In particular, the 蟻(T) dependences show the shallow minimum at T_min 鈭?#xA0;35 K and 鈭?0 K for Na- and Ba-doped samples, respectively. Application of the external H up to 8 T leads to marked flattening of such minimum and to notable lowering of the T_min on 蟻(T,H) curves. The authors attributed this low temperature anomaly to competitive quantum Kondo effect and three-dimensional electron-electron interaction, using the results of numerical fittings of 蟻 versus T and H dependences in the interval of about 5-50 K. It is suggested in the comment that such a claim seems to be doubtful due to the fundamental inapplicability of this approach for analysis of low temperature conductivity in polycrystalline manganites. It is noted that a natural reason for the both, the low temperature minimum on 蟻(T) curve and its evolution upon magnetic field application, is the well known grain boundary effects.