Structure, electron-transport properties, and giant magnetoresistance of hole-doped LaMnO3 systems

Mahendiran, R. ; Tiwary, S. K. ; Raychaudhuri, A. K. ; Ramakrishnan, T. V. ; Mahesh, R. ; Rangavittal, N. ; Rao, C. N. R. (1996) Structure, electron-transport properties, and giant magnetoresistance of hole-doped LaMnO3 systems Physical Review B: Condensed Matter and Materials Physics, 53 (6). pp. 3348-3358. ISSN 1098-0121

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Official URL: http://link.aps.org/doi/10.1103/PhysRevB.53.3348

Related URL: http://dx.doi.org/10.1103/PhysRevB.53.3348

Abstract

Results of a detailed investigation of the structure and electron-transport properties of La1-xAxMnO3 (A=Ca, Sr) over a wide range of compositions are presented along with those of parent LaMnO3 containing different percentages of Mn4+. The electrical resistivity (ρ) and magnetoresistance (MR) of polycrystalline pellets have been measured in the 4.2-400 K range in magnetic fields up to 6 T and the Seebeck coefficient (S) from 100 to 400 K. The electrical measurements were supplemented by ac susceptibility and magnetization measurements. MR is large and negative over a substantial range of compositions and peaks around temperatures close to the ferromagnetic transition temperatures (Tc). An insulator to metal-like transition occurs near the Tc and the temperature dependence of ρ below Tc is related to the magnetization although ρ in the metallic state is generally much larger than the Mott's maximum metallic resistivity. The occurrence of giant magnetoresistance is linked to the presence of an optimal proportion of Mn4+ ions and is found in the rhombohedral and the cubic structures where the Mn-O distance is less than 1.97 Å and the Mn-O-Mn angle is 170° ± 10°. The field dependence of MR shows the presence of two distinct regimes. The thermopower S shows a positive peak in the composition range at a temperature where MR also peaks; S becomes more negative with increase in Mn4+.

Item Type:Article
Source:Copyright of this article belongs to The American Physical Society.
ID Code:40796
Deposited On:29 Jun 2011 13:08
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