Effects of inhomogeneous oxygen content in (La,Gd)0.7Ca0.3MnO3+δ perovskites

Sun, J. R.; Rao, Guanghui; Zhang, Y. Z.

doi:10.1063/1.121551

Cited by 53 publications

(27 citation statements)

References 17 publications

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“…Gebhardt et al [28] have shown that the chemical inhomogeneity is the origin of the double peak in resistivity behavior of their samples. Sun et al [29] have shown that the oxygenation inhomogeneity leads to a double peak behavior. In these cases, the compositional disorder occurs in the scale of the whole sample and not in each grain as in the case of small grain size samples.…”

Section: Resultsmentioning

confidence: 98%

Structural, magnetic and magnetotransport properties of La0.8Sr0.2MnO3/xLaMnO3 composites

Kameli¹,

Salamati²,

Hakimi³

2008

Journal of Alloys and Compounds

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Section: Resultsmentioning

confidence: 98%

Structural, magnetic and magnetotransport properties of La0.8Sr0.2MnO3/xLaMnO3 composites

Kameli¹,

Salamati²,

Hakimi³

2008

Journal of Alloys and Compounds

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“…According to Sun et al's [30] work, when fabricating the sample of La 0.72−x Gd x Ca 0.3 Mn y O 3+δ by solid-state reaction, the different activities of La 2 O 3 and La(OH) 3 leaded to inhomogeneous distribution of oxygen content in the compound, which caused two peak of the ρ -T curves. Wu et al [19] also confirmed that the double peak shown in ρ -T curves of La 0.9 MnO 3+δ were closely related to the oxygen content.…”

Section: Resultsmentioning

confidence: 98%

Anomalous magnetotransport in LaMn1−x Te x O3

Tan

Chen

Zhang

2009

Sci. China Ser. G-Phys. Mech. Astron.

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The LaMn 1−x Te x O 3+δ (x=0.1, 0.2, 0.3) were synthesized using solid-state reaction method for the first time. X-ray photoemission spectrum (XPS) shows that in the samples the Te ions have a valence of Te 4+ , and Mn 3+ ions are partly converted into Mn 2+ and Mn 4+ due to the excess oxygen and Te doping. The magnetotransport associated with Mn 2+ , Mn 3+ and Mn 4+ was investigated. The experimental results show that the samples are insulator at 0 T when the amount of Mn 3+ is much larger or less than the sum of Mn 2+ and Mn 4+ ; by contrast, the samples display metal to insulator transition with increasing temperature when the amount of Mn 3+ is close to the sum of Mn 2+ and Mn 4+ . These anomalous magnetotransport behaviors were analyzed in the frame of the double-exchange (DE) mechanism.colossal magnetoresistance, La-Te-Mn-O, magnetotransport Doped LaMnO 3 have been widely studied due to a rich variety of physical properties [1][2][3][4] . The prominent one is the colossal magnetoresistance (CMR) effect, a phenomenon of the resistive transition induced by the magnetic transition, and CMR is traditionally explained by the double exchange (DE) [5] interaction. The key role in DE mechanism is played by Mn ions, the unique magnetic ions in LaMnO 3 , which affect not only the transport behaviors of manganites by the network of Mn-OMn, but also the magnetism of materials by the spin variation of Mn ions.As demonstrated by numerous studies, the valence of Mn ions in the manganites varies with the dopant, which is considered the intrinsic factor to understanding CMR effect. Mn ions are usually all trivalent (Mn 3+ ) in LaMnO 3 .When La ions were substituted partially by divalent ions, such as Ca 2+ , Sr 2+ etc., some Mn 3+ would convert into Mn 4+ , and Mn 3+ -Mn 4+ mixed valences are formed in the stable manganites of La 1−x A x MnO 3 [5][6][7][8] .When La ions were substituted partially by tetravalent ions, such as Ce 4+ , Te 4+ ... etc., some Mn 3+ would convert into Mn 2+ , which leads to the Mn 2+ -Mn 3+ mixed valence in La 1−x A x MnO 3 (A=Ce 4+ , Te 4+ ...) [8,9] . The interactions between Mn 4+ (or Mn 2+ ) ions and the neighboring Mn 3+ ions via O 2− are believed to contribute to the DE effect.The influence of the La-site substitution in manganites on DE mechanism is indirect, depending on the conversion of Mn 3+ ions. The direct influence, undoubtedly, is the Mn-site substitution. Recently, most studies on the Mn-site substitution focus on the La 1−x A x MnO 3 or LaMnO 3 . It is found that the manganites with the formula of La 1−x A x Mn 1−y O 3 (A=Ca 2+ , Sr 2+ ...; M=Zr 2+ , Cr 3+ , Ta 4+ ,...) or LaMn 1−x B x O 3 (B=T 4+ , Mo 6+ ...) still remain Mn 3+ -Mn 4+ (or Mn 3+ -Mn 2+ ) mixed-valence, and undergo ferro-to para-magnetism (FM-PM) transition. However, both have the different magnetotransport behavior.

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“…-Other authors [42] deliberately used a mixture of La(OH) 3 and La 2 O 3 as source of lanthanum and obtained double peaks. But our La 2 O 3 was calcined before use.…”

Section: Resultsmentioning

confidence: 99%

Effects of silicon addition on the electrical and magnetic properties of copper-doped (La,Ca)MnO3 compounds

Vertruyen

Rulmont

Cloots

et al. 2004

Journal of Magnetism and Magnetic Materials

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In this paper we report about the electrical properties of La 0.7 Ca 0.3 MnO 3 compounds substituted by copper on the manganese site and/or deliberately contaminated by SiO 2 in the reactant mixture. Several phenomena have been observed and discussed. SiO 2 addition leads to the formation of an apatite-like secondary phase that affects the electrical conduction through the percolation of the charge carriers. On the other hand, depending on the relative amounts of copper and silicon, the temperature dependence of the electrical resistivity can be noticeably modified : our results enable us to compare the effects of crystallographic vacancies on the A and B sites of the perovskite with the influence of the copper ions substituted on the manganese site. The most original result occurs for the compounds with a small ratio Si/Cu, which display double-peaked resistivity vs. temperature curves.

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Effects of inhomogeneous oxygen content in (La,Gd)0.7Ca0.3MnO3+δ perovskites

Cited by 53 publications

References 17 publications

Structural, magnetic and magnetotransport properties of La0.8Sr0.2MnO3/xLaMnO3 composites

Structural, magnetic and magnetotransport properties of La0.8Sr0.2MnO3/xLaMnO3 composites

Anomalous magnetotransport in LaMn1−x Te x O3

Effects of silicon addition on the electrical and magnetic properties of copper-doped (La,Ca)MnO3 compounds

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