Ferromagnetism and large negative magnetoresistance in Bi1−xCaxMnO3 (x ≥ 0.8) perovskite

Chiba, Hiroshi; Kikuchi, Michio; Kusaba, Keiji; Muraoka, Yuji; Syono, Yasuhiko

doi:10.1016/0038-1098(96)00305-5

Cited by 120 publications

(102 citation statements)

References 9 publications

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“…The inset of Fig. 2(a) shows the intensities at 10 K after subtracting the background scattering at 200 K, and a fit to a power-law behavior, I = AQ −5.4 (2) , for Q between 0.007Å −1 and 0.025Å −1 . This result indicates the existence of magnetic domains with sizes of several hundred Angstroms or larger, evidencing a long-range FM component.…”

Section: Results and Analysismentioning

confidence: 99%

“…Electron-doped CaMnO 3 samples are particularly attractive model systems due to the relative simplicity and chemical stability of the parent compound, which shows a simple quasi-cubic crystal structure and an isotropic G-AFM spin ground state 1 . For electrondoped CaMnO 3 , a relatively weak ferromagnetism has been observed up to ∼ 15 % doping 2,3,4,5,6 . While the classic de Gennes theory for lightly-doped manganites describes the weak ferromagnetism in terms of spin-canted ground states 7 , a number of more recent theoretical studies indicate that homogeneous canted magnetic structures may not be energetically stable, suggesting a tendency towards magnetic and electronic phase segregation for both hole-doped 8,9,10,11,12,13,14,15,16,17 and electrondoped 14,15,16,17,18 manganites.…”

Section: Introductionmentioning

confidence: 99%

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Inhomogeneous magnetism in La-dopedCaMnO3. II. Nanometric-scale spin clusters and long-range spin canting

et al. 2003

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Neutron measurements on Ca1−xLaxMnO3 (0.00 ≤ x ≤ 0.20) reveal the development of a liquidlike spatial distribution of magnetic droplets of average size ∼ 10Å, the concentration of which is proportional to x (one cluster per ∼ 60 doped electrons). In addition, a long-range ordered ferromagnetic component is observed for 0.05 x 0.14. This component is perpendicularly coupled to the simple G-type antiferromagnetic (G-AFM) structure of the undoped compound, which is a signature of a G-AFM+FM spin-canted state. The possible relationship between cluster formation and the stabilization of a long-range spin-canting for intermediate doping is discussed.

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Section: Results and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Inhomogeneous magnetism in La-dopedCaMnO3. II. Nanometric-scale spin clusters and long-range spin canting

et al. 2003

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“…25 Ca 0.75 MnO 3 are characterized by charge ordering phenomena and do not exhibit magnetoresistive effects. However the recent discovery of new ferromagnetic electron doped manganites, Ca 1−x B x MnO 3 and Ca 1−x Bi x MnO 3 for x = 0.10 [14,15], has increased the interest for those compounds since it opens the possibility of magnetoresistance effects also in this concentration limit. Ca 0.9 Bi 0.1 MnO 3 and Ca 0.9 Eu 0.1 MnO 3 exhibit indeed negative magnetoresistance but with a much smaller magnitude than hole doped manganites.…”

Section: Introductionmentioning

confidence: 99%

Ferromagnetic polarons in manganites

et al. 2000

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Using the Lanczos method in linear chains we study the double exchange model in the low concentration limit, including an antiferromagnetic super-exchange K. In the strong coupling limit we find that the ground state contains ferromagnetic polarons whose length is very sensitive to the value of K/t. We investigate the dispersion relation, the trapping by impurities, and the interaction between these polarons. As the overlap between polarons increases, by decreasing K/t, the effective interaction between them changes from antiferromagnetic to ferromagnetic. The scaling to the thermodynamic limit suggests an attractive interaction in the strong coupling regime (J h > t) and no binding in the weak limit (J h ≃ t).

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“…Hence, the same activity tests were repeated while analysing the effluent gas by 9 gas-chromatography, in order to check data accuracy. The results were comparable within 10°C.…”

Section: Catalytic Activitymentioning

confidence: 99%

“…Indeed, perovskite catalysts combine low cost, thermo-chemical stability at high operating temperature and satisfactory catalytic activity [5][6][7][8]. Interest is growing for these materials because of their interesting transport properties [9][10][11][12][13][14][15][16][17][18][19][20], such as oxygen mobility, important for their activity as catalysts in the catalytic flameless combustion of methane [18][19][20] and for solid oxide fuel cells. Transport properties are strongly dependent on 6 1h, by flowing 40 cm3/min of 10 vol% H 2 in He gas mixture and by increasing temperature from r.t. up to 800°C by 10°C/min.…”

Section: Introductionmentioning

confidence: 99%

Perovskite-like catalysts for the catalytic flameless combustion of methane

2012

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QUESTIONNAIREThe catalytic flameless combustion (CFC) of methane outperforms conventional flame combustion because of lower emission of pollutants (HC, CO and NO x ) and high thermal efficiency. The catalysts traditionally used for CFC are mainly based on supported noble metals, such as Pd and Pt, which ensure high activity, however accompanied by some drawbacks, due to high cost and poor thermal and chemical stability. La-based catalysts with ABO 3 perovskite-like structure have been proposed as a valid alternative for the present application. Indeed, perovskite catalysts combine low cost, thermochemical stability at high operating temperature and satisfactory catalytic activity. In spite of this, there are still some open questions, especially regarding their resistance to sulphur poisoning when used for the CFC of methane. Indeed, the poisoning mechanism of perovskite-like catalysts has not been completely understood and only a few papers deal with this very important topic.In general, the partial substitution of the perovskitic lattice metal ions is one of the important means to modulate catalytic activity. In LaBO 3 perovskites, the influence of dopants such as A' 2+ and A' 4+ has been widely investigated in the literature.* Corresponding author: fax +39-02-50314300; e-mail ilenia.rossetti@unimi.it 2In the recent past, attention has been devoted to catalyst nanostructuring, aiming at obtaining high surface area and defectivity, which should enhance oxygen mobility through the lattice and ensure good catalytic activity. To this purpose, we set up and optimised a flame-pyrolysis (FP) apparatus for the onestep synthesis of perovskitic mixed oxides. It is based on a specially designed burner fed with oxygen and an organic solution of the precursors, the solvent acting as fuel for the flame. FP-synthesized perovskites, showed good phase purity, along with nanometer-size particles and hence very high surface area (sometimes in excess of 100 m 2 /g). In addition, the high temperature of the flame in principle should also ensure thermal stability.In the present work we prepared a set of samples by FP, namely La 1-x A x MeO 3 , with A' = Ce, Sr, Ag Me=Mn, Co, x=0, 0.1, 0.2, either pure or doped with noble metals (Pt, Pd or Ag). In addition silver containing samples were synthesized by a traditional sol-gel (SG) method. The catalysts were tested for the CFC of methane, monitoring the activity by online mass spectrometry. Also the resistance to sulphur poisoning was investigated, using tetrahydrothiophene as poisoning agent.

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Ferromagnetism and large negative magnetoresistance in Bi1−xCaxMnO3 (x ≥ 0.8) perovskite

Cited by 120 publications

References 9 publications

Inhomogeneous magnetism in La-dopedCaMnO3. II. Nanometric-scale spin clusters and long-range spin canting

Inhomogeneous magnetism in La-dopedCaMnO3. II. Nanometric-scale spin clusters and long-range spin canting

Ferromagnetic polarons in manganites

Perovskite-like catalysts for the catalytic flameless combustion of methane

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