Field-induced orbital patterns in ferromagnetic layered ruthenates

Forte, Filomena; Cuoco, Mario; Noce, Canio

doi:10.1103/physrevb.82.155104

Cited by 24 publications

(15 citation statements)

References 44 publications

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“…We also carried out the calculation of the local and two-site orbital angular momentum correlation functions, which reveal that the A peak in the AFM case has significant orbital contribution, while it is substantially suppressed in the FM case. This is consistent with the observation that the FM ground state has a different orbital pattern [50] when compared to the AFM configuration. The doublon can have a stronger tendency to occupy different orbitals on neighboring Ru sites in the FM case.…”

Section: Ca 2 Ruo 4 No Dispersion Was Resolved For the Corresponding supporting

confidence: 92%

Resonant inelastic x-ray scattering study of Ca3Ru2O7

et al. 2020

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We present a combined oxygen K-edge x-ray absorption spectroscopy and resonant inelastic x-ray scattering (RIXS) study of the bilayer ruthenate Ca 3 Ru 2 O 7. Our RIXS experiments on Ca 3 Ru 2 O 7 were carried out on the overlapping planar and interplanar oxygen resonances, which are distinguishable from the apical one. Comparison to equivalent oxygen K-edge spectra recorded on band-Mott insulating Ca 2 RuO 4 is made. In contrast to Ca 2 RuO 4 spectra, which contain excitations linked to Mott physics, Ca 3 Ru 2 O 7 spectra feature only intra-t 2g ones that do not directly involve the Coulomb energy scale. As found in Ca 2 RuO 4 , we resolve two intra-t 2g excitations in Ca 3 Ru 2 O 7. Moreover, the lowest lying excitation in Ca 3 Ru 2 O 7 shows a significant dispersion, revealing a collective character different from what is observed in Ca 2 RuO 4. Theoretical modeling supports the interpretation of this lowest energy excitation in Ca 3 Ru 2 O 7 as a magnetic transverse mode with multiparticle character, whereas the corresponding excitation in Ca 2 RuO 4 is assigned to combined longitudinal and transverse spin modes. These fundamental differences are discussed in terms of the inequivalent magnetic ground-state manifestations in Ca 2 RuO 4 and Ca 3 Ru 2 O 7 .

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Section: Ca 2 Ruo 4 No Dispersion Was Resolved For the Corresponding supporting

confidence: 92%

Resonant inelastic x-ray scattering study of Ca3Ru2O7

et al. 2020

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“…In particular, it was reported that the imaginary part of the bare electron susceptibility of K 2 Cr 3 As 3 shows large peaks at the point Γ, suggesting the presence of large ferromagnetic spin fluctuations in the compound 36 , that are robust and persist in the case of non-equilateral triangles. We note that these results suggest an analogy with the ruthenates [56][57][58][59][60][61][62][63] . Indeed, the compound Ca 2 RuO 4 is magnetic with an antiferromagnetic coupling between the Ru-ions, 64 whereas Sr 2 RuO 4 in on the verge of magnetism, exhibiting in the magnetic phase a ferromagnetic coupling among the Ru-ions.…”

Section: Discussionsupporting

confidence: 52%

Intrachain collinear magnetism and interchain magnetic phases in Cr3As3−K -based materials

et al. 2021

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We perform a comparative study of the KCr3As3 and the K2Cr3As3 quasi 1D compounds, and show that the strong interplay between the lattice and the spin degrees of freedom promotes a new collinear ferrimagnetic ground state within the chains in presence of intrachain antiferromagnetic couplings. We propose that the interchain antiferromagnetic coupling in KCr3As3 plays a crucial role for the experimentally observed spin-glass phase with low critical temperature. In the same region of the parameter space, we predict K2Cr3As3 to be non-magnetic but on the verge of the magnetism, sustaining interchain ferromagnetic spin fluctuations while the intrachain spin fluctuations are antiferromagnetic.

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“…Similar values for ∆, U and J H have been used for band structure calculations in Ca 2 RuO 4 14 , while a ratio |∆|/λ in the range ∼ 3 − 4 was found to correctly reproduce the spin excitations observed by inelastic neutron scattering 11 . For the hopping amplitudes, we considered a representative set of electronic parameters for the Ru-O-Ru cluster that is consistent with typical amplitudes obtained from first-principle calculations on ruthenium oxides 7,15,38,[47][48][49] . Given the limited impact of La substitution on the Ru-O-Ru bond angle and octahedral tilt away from the c axis 16 , we assumed that the hopping amplitudes are not quantitatively affected by the La concentration.…”

Section: Theoretical Calculationsmentioning

confidence: 99%

Tuning of the Ru4+ ground-state orbital population in the 4d4 Mott insulator C

et al. 2019

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The ground-state orbital occupancy of the Ru 4+ ion in Ca2−xLaxRuO4 [x = 0, 0.05(1), 0.07(1) and 0.12(1)] was investigated by performing X-ray absorption spectroscopy (XAS) in the vicinity of the O K edge as a function of angle between the incident beam and the surface of the single-crystal samples. A minimal model of the hybridization between the O 2p states probed at the K edge and the Ru 4d orbitals was used to analyze the XAS data, allowing the ratio of hole occupancies nxy/nyz,zx to be determined as a function of doping and temperature. For the samples displaying a low-temperature insulating ground-state (x ≤ 0.07), nxy/nyz,zx is found to increase significantly with increasing doping, with increasing temperature acting to further enhance nxy/nyz,zx. For the x = 0.12 sample, which has a metallic ground-state, the XAS spectra are found to be independent of temperature, and not to be describable by the minimal hybridization model, while being qualitatively similar to the spectra displayed by the x ≤ 0.07 samples above their insulating to metallic transitions. To understand the origin of the evolution of the electronic structure of Ca2−xLaxRuO4 across its phase diagram, we have performed theoretical calculations based on a model Hamiltonian, comprising electron-electron correlations, crystal field (∆) and spin-orbit coupling (λ), of a Ru-O-Ru cluster, with realistic values used to parameterize the various interactions taken from the literature. Our calculations of the Ru hole occupancy as a function of ∆/λ provide an excellent description of the general trends displayed by the data. In particular they establish that the enhancement of nxy/nyz,zx is driven by significant modifications to the crystal field as the tetragonal distortion of the RuO6 octahedral changes from compressive to tensile with La doping. We have also used our model to show that the hole occupancy of the O 2p and Ru 4d orbitals display the same general trend as a function of ∆/λ, thus validating the minimal hybridization model used to analyze the data. In essence, our results suggest that the predominant mechanism driving the emergence of the low-temperature metallic phase in La doped Ca2RuO4 is the structurally induced redistribution of holes within the t2g orbitals, rather that the injection of free carriers.

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Field-induced orbital patterns in ferromagnetic layered ruthenates

Cited by 24 publications

References 44 publications

Resonant inelastic x-ray scattering study of Ca3Ru2O7

Resonant inelastic x-ray scattering study of Ca3Ru2O7

Intrachain collinear magnetism and interchain magnetic phases in Cr3As3−K -based materials

Tuning of the Ru4+ ground-state orbital population in the 4d4 Mott insulator C

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