Magnetic Properties of REMe0.5Mn0.5O3(RE = Rare Earth Element, Me = Ni, Co)

“…This is not inconsistent with the magnetization results of Asai et al, 16 if we make an extrapolation to higher magnetic fields as to estimate the saturated total moment. Our result is larger than the neutron results, but also not inconsistent if one is willing to accept that there is an appreciable amount of Co-Mn disorder in the neutron sample.…”

Section: 38supporting

confidence: 82%

Local electronic structure and magnetic properties ofLaMn0.5Co0.5O3studied by x-ray absorption and magnetic circular dichroism spectroscopy

et al. 2008

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We have studied the local electronic structure of LaMn0.5Co0.5O3 using soft-x-ray absorption spectroscopy at the Co-L3,2 and Mn-L3,2 edges. We found a high-spin Co 2+ -Mn 4+ valence state for samples with the optimal Curie temperature. We discovered that samples with lower Curie temperatures contain low-spin nonmagnetic Co 3+ ions. Using soft-x-ray magnetic circular dichroism we established that the Co 2+ and Mn 4+ ions are ferromagnetically aligned. We revealed also that the Co 2+ ions have a large orbital moment: m orb /mspin ≈ 0.47. Together with model calculations, this suggests the presence of a large magnetocrystalline anisotropy in the material and predicts a nontrivial temperature dependence for the magnetic susceptibility.PACS numbers: 71.27.+a, 78.70.Dm, 75.25.+z The manganites continue to attract considerable attention from the solid state physics and chemistry community over the last five decades because of their spectacular material properties.1,2,3,4 The parent compound LaMnO 3 is an A-type antiferromagnetic insulator with orthorhombic perovskite crystal structure. Replacing La by Sr, Ca or Ba results in multifarious electronic and magnetic properties including the transformation into a ferromagnetic state accompanied by a metal-insulator transition and the occurrence of colossal magnetoresistance.5,6 Substitution of the magnetic Mn ions by Co also yields ferromagnetism in the LaMn 1−x Co x O 3 series. The Curie temperature reaches a maximum for x = 0.5 (T C = 220-240 K). 7,8,9,10,11 This should be contrasted with the end member of this series, namely the rhombohedral LaCoO 3 , which is a nonmagnetic insulator at low temperatures, showing yet the well-known spin-state transition at higher temperatures which by itself is subject of five decades of intensive study. 7,9,12 Explaining the appearance of ferromagnetism in the manganites by Co substitution is, however, not a trivial issue. Assuming that ordering of the Co and Mn ions had not been achieved for the x = 0.5 composition, Goodenough et al. concluded early on that the ferromagnetism is generated by Mn 3+ -O-Mn 3+ superexchange interactions.7 On the other hand, later magnetic susceptibility and Mn NMR studies suggested that it is the exchange interaction involving the ordering of Co 2+ -Mn 4+ transition-metal ions which causes the ferromagnetism in LaMn 0.5 Co 0.5 O 3 . 8,9,13,14,15,16,17 Only few high-energy spectroscopic studies are reported for the Co substituted manganites. Using soft-xray absorption spectroscopy (XAS), Park et al. found in their low Co compositions that the Co ions are divalent, favoring a Mn 3+ -Mn 4+ double-exchange mechanism for the ferromagnetism.18 Extrapolating this Co divalent result to the x = 0.5 composition would provide support to the suggestion that the ferromagnetism therein is caused by the Co 2+ -Mn 4+ exchange interaction. However, no XAS data have been reported so far for this x = 0.5 composition. Using K-edge XAS, Toulemonde et al. revealed that the Co ion is also divalent in their hole doped and Co sub...

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“…The cooperative Jahn-Teller effect that leads to orbital and spin orderings in LaMnO 3 is perturbed when a spherical d 10 ion is substituted on the manganese site. The antiferromagnetic structure is progressively destroyed while the ferromagnetic component becomes larger.…”

Section: Discussionmentioning

confidence: 99%

“…In the first case [6][7][8], the effect of the Mn site substitution is studied in the double exchange background induced by the Ln site substitution. In the second case [9][10][11], the doping cation interferes with the superexchange interactions present in the LnMnO 3 parent compounds. In this work we have chosen to study the gallium substitution on the manganese site of LaMnO 3 .…”

Section: Introductionmentioning

confidence: 99%

Magnetic properties of Ga-doped lanthanum manganite with controlled oxygen stoichometry

Vertruyen

Hébert

Maignan

et al. 2002

Crystal Engineering

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Stoichiometric LaMnO 3 is an insulator whose A-type antiferromagnetic structure at low temperature is mainly connected to the Jahn-Teller distortion of the MnO 6 octahedra. The substitution of non magnetic d 10 Ga 3+ ions on the manganese site disrupts the orbital and spin orderings of the manganese ions and has a strong influence on the physical properties. The antiferromagnetic order is progressively destroyed while the ferromagnetic component increases. At the same time, the distortion of the orthorhombic cell decreases and the high temperature structural Jahn-Teller transition disappears. Such studies on manganese site substitutions give insight into the physics of the Mn-O three-dimensional network, which is supposed to be the key feature in the CMR manganites.

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Magnetic Properties of REMe_0.5Mn_0.5O₃(RE = Rare Earth Element, Me = Ni, Co)

Cited by 91 publications

References 16 publications

Synthesis, Crystal Structure, and Magnetic Properties of Quasi-One-Dimensional Oxides Ca3CuMnO6 and Ca3Co1+xMn1−xO6

Synthesis, Crystal Structure, and Magnetic Properties of Quasi-One-Dimensional Oxides Ca3CuMnO6 and Ca3Co1+xMn1−xO6

Local electronic structure and magnetic properties ofLaMn0.5Co0.5O3studied by x-ray absorption and magnetic circular dichroism spectroscopy

Magnetic properties of Ga-doped lanthanum manganite with controlled oxygen stoichometry

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