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Rettori, C.; Rao, D.; Singley, Joseph M.; Kidwell, David A.; Oseroff, S. B.; Causa, M.T.; Neumeier, J. J.; McClellan, K. J.; Cheong, S. W.; Schultz, S.

doi:10.1103/physrevb.55.3083

Cited by 121 publications

(71 citation statements)

References 40 publications

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“…The increase of the resonance linewidth at high temperatures may be explained by the temperature dependence of relaxation processes above the Curie temperature. As seen in Figure 4, the temperature dependence of the ESR resonance linewidth provides a minimum in H PP , located at 270 K. The minimum in the temperature dependence of the resonance linewidth occurs at a temperature T=1.1T C [7][8][9][10][11], and this is close to a Curie temperature of about 250 K. The resonance linewidth, in the magnetically ordered phase decreases as the temperature of the sample is raised towards the Curie temperature. It was noted [9] that the resonance linewidth is proportional to the magnetization at saturation.…”

Section: Discussionmentioning

confidence: 89%

“…The coexistence of ferromagnetic and paramagnetic domains, in a temperature range close to Curie temperature was discussed by Borges and collaborators [11]. The resonance spectra in the paramagnetic phase (see for example in Figure 2 the spectrum recorded at T = 261 K) consist of a narrow line, slightly asymmetric, localized near the g=2.00 value, ascribed to a cluster including both Mn4 + and Mn3 + ions [7][8][9][10]. The absence of the hyperfine structure, due to the interaction between the uncoupled electronic spin and the nuclear ones is explained by motional effects and/or exchange interactions.…”

Section: Discussionmentioning

confidence: 99%

“…If the size of the particle is smaller or equal to the skin depth of the microwave field, then this leads to field damping within the sample causing a particular asymmetric line, known as a Dysonian line. As the estimated skin depth in perovskites for X band measurements is of the order of 0.1 mm [8][9], the contribution of this process to the resonance line asymmetry is small. The mixing of absorption and dispersion, frequently noticed in the magnetic ordered phase [7], represents the second contribution to line shape anisotropy.…”

Section: Discussionmentioning

confidence: 99%

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ESR investigations on Ca perovskite

et al. 2000

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Electron spin resonance studies on fine powders of La 0.65 Ca 0.35 MnO 3 , performed in the X band, are reported. The coexistence of paramagnetic and ferromagnetic phases, in a narrow temperature range close to the Curie temperature, is observed. The electron spin resonance measurements do not support the presence of bipolarons above the Curie temperature. Temperature dependence of the ESR linewidth is governed by the hopping of polarons and the corresponding activation energy is about 150 meV above T C .

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Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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ESR investigations on Ca perovskite

et al. 2000

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“…Electron paramagnetic resonance (EPR) has been studied in a variety of lanthanum manganites. Some authors [4,5] attributed the temperature dependence of the EPR linewidth to a spin-phonon interaction (one-phonon relaxation process) and explained it by spin-lattice relaxation of exchange coupled Mn …”

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confidence: 99%

Adiabatic polaron transport in La_0.9Pb_0.1MnO₃ manganites

Ulyanov

Quang

Vasundhara

et al. 2004

Physica Status Solidi (b)

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A study of single-phase La 0.9 Pb 0.1 MnO 3 compositions is presented. The temperature dependence of the EPR line intensity and resistivity evidence a spin-lattice interaction in the paramagnetic region near the Curie point. In the high temperature region a spin-spin interaction is dominant. is not yet clear enough despite a large number of publications on this problem. The difficulties consist in a close connection between structure, electronic and magnetic properties of perovskite-type manganites. Resonance methods can give useful information about the internal dynamics of these materials, especially near the Curie temperature, T C , where they show the highest value of the CMR effect. Electron paramagnetic resonance (EPR) has been studied in a variety of lanthanum manganites. Some authors [4,5] attributed the temperature dependence of the EPR linewidth to a spin-phonon interaction (one-phonon relaxation process) and explained it by spin-lattice relaxation of exchange coupled Mn

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“…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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Temperature dependence of the ESR linewidth in the paramagnetic phase (T>TC) ofR1

Cited by 121 publications

References 40 publications

ESR investigations on Ca perovskite

ESR investigations on Ca perovskite

Adiabatic polaron transport in La_0.9Pb_0.1MnO₃ manganites

Perovskite-like catalysts for the catalytic flameless combustion of methane

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Temperature dependence of the ESR linewidth in the paramagnetic phase (T>TC) ofR1

Cited by 121 publications

References 40 publications

ESR investigations on Ca perovskite

ESR investigations on Ca perovskite

Adiabatic polaron transport in La0.9Pb0.1MnO3 manganites

Perovskite-like catalysts for the catalytic flameless combustion of methane

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Product

Resources

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Adiabatic polaron transport in La_0.9Pb_0.1MnO₃ manganites