Infrared study of crystal-field excitations in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Nd</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn><mml:mi>−</mml:mi><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">Ce</mml:mi></mml:mrow><mml:mrow><mml:mi>x</mml:mi></mml:mrow></mml:msub></mml:mrow><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">CuO</mml:mi>

Jandl, S.; Richard, P.; Poirier, M.; Nekvasil, V.; Nugroho, A. A.; Menovsky, A.A.; Zhigunov, D. I.; Barilo, S. N.; Shiryaev, S. V.

doi:10.1103/physrevb.61.12882

Cited by 14 publications

(33 citation statements)

References 25 publications

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“…Assuming a perfect orientation of the crystal and the absence of depolarization effects as well as of disorder, ⌫ i →⌫ i (iϭ1, 2, 3, 4, 5͒ dipole transitions are allowed for Eʈc while ⌫ 5 →⌫ 1 , ⌫ 2 , ⌫ 3 , and ⌫ 4 dipole transitions are allowed for EЌc. 23,12 As was found for undoped and cerium-doped Nd 2 CuO 4 and Pr 2 CuO 4 crystals, 9,11 more infrared absorption bands are observed than expected from the Pr 3ϩ regular sites. The additional absorption bands are due to nonregular Pr 3ϩ sites, Table I.…”

Section: Resultsmentioning

confidence: 77%

“…7,8 Particularly, Raman scattering and infrared transmission spectroscopies have proven to be valuable techniques in the determination of the rare-earth CF excitations in both electron-doped [9][10][11][12] and hole-doped cuprates. 13,14 Since the rare-earth ions are surrounded by oxygen ions, defects such as oxygen vacancies and interstitial oxygens affect their CF energy levels.…”

Section: Introductionmentioning

confidence: 99%

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Pr3+crystal-field excitation study of apical oxygen and reduction processes inPr2−

et al. 2004

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We present an infrared transmission Pr 3ϩ crystal-field study of as-grown, reduced, and oxygenated Pr 2Ϫx Ce x CuO 4Ϯ␦ single crystals and thin films. Excitations from the ground-state multiplet 3 H 4 to the 3 H 5 , 3 H 6 , 3 F 2 , and 3 F 3 excited multiplets are observed in all samples. In addition to the Pr 3ϩ regular sites, which remain unperturbed following the cerium doping or the oxygen content modifications, Pr 3ϩ sites are detected. A precise set of crystal-field parameters, which reproduces the energy and the symmetry of the levels, is determined. The reduction process, which drives the electron-doped cuprates superconducting, is discussed in detail and scenarios for the reduction mechanism and induced vacancies are proposed. In contrast to the common belief, the apical oxygen, which is clearly detected in all samples, is not removed in Pr 1.85 Ce 0.15 CuO 4 following reduction. This observation questions the role attributed to the apical oxygen removal in triggering the superconductivity.

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Section: Resultsmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Pr3+crystal-field excitation study of apical oxygen and reduction processes inPr2−

et al. 2004

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“…18 More recently, acoustic measurements at lower frequencies performed on polycrystalline NCCO bars revealed a softening of the Young's modulus below 20 K. 19 Because Ce doping shifts this anomaly to lower tempera-tures, the authors concluded that it could not be related to the minimum observed in C 66 ͑T͒ in the ultrasonic experiments performed on single crystals. 16,17 The authors interpreted rather this anomaly in terms of a paraelastic contribution from the relaxation of Nd 3+ 4f electrons between the levels of the ground state doublet split by the interaction with the antiferromagnetically ordered Cu 2+ lattice; the value of the splitting was then found to be in agreement with inelastic neutron scattering, 20 infrared transmission, 21 and specific heat experiments. 22 In this paper, we further investigate the magnetic properties of Nd 2 CuO 4 at low temperature with the ultrasonic technique.…”

Section: Introductionmentioning

confidence: 81%

Low-temperature magnetism ofNd2CuO4: An ultrasonic investigation

2005

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We have performed an ultrasonic study of Nd 2 CuO 4 in order to investigate the low temperature magnetism due to the Nd 3+ moments. In addition to small anomalies corresponding to the Cu 2+ spin reorientations observed at 33 and 67 K, a large magnetic field and frequency dependent anomaly is detected around 4 K in the C 66 elastic constant and the corresponding attenuation variations. The frequency dependence of this anomaly, which disappears under a magnetic field of 2 T applied along the in-plane Cu-O bonds, is related to a resonant phenomenon rather than to a phase transition as previously reported. The ultrasonic measurements suggest the development of local domains, due to a frustration of the magnetic structure caused by the competition between the Nd 3+ -Cu 2+ and the Nd 3+ -Nd 3+ interactions at low temperature. In contrast to the common belief, the C 66 elastic constant and attenuation anomalies above 2 T characterize a field-induced transition of the Nd 3+ spins which occurs at critical field lower than the one associated with the Cu 2+ spins.

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“…Electron Raman scattering and infrared (IR) absorption provided a powerful experimental tool to study the crystal-field (CF) excitations in Nd 2−x Ce x CuO 4 [1][2][3][4]. They complement inelastic neutron experiments (see ref.…”

Section: Introductionmentioning

confidence: 99%