Crystal-field splittings of gadolinium (4<i>f</i>7) levels in <i>C</i>-type rare earth oxides

Antić-Fidančev, E.; Lemaı̂tre-Blaise, M.; Caro, P.

doi:10.1063/1.443372

Cited by 36 publications

(28 citation statements)

References 14 publications

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“…These results do not change , significantly even when the other data sets complied by Blume et al (1964) and the data in later publications for Ln3+ crystalline compounds or Ln3" doped in various crystals are used (Carnal et al, 1972 andCrosswhite et al, 1976 and1977;Foster et al, 1985a, b;Morley et al, 1981Antic-Fidancev et al, 1982;' Huang et al, 1984). Blume et al (1964).…”

Section: Screening Constant and A New Rspet Formulationsupporting

confidence: 50%

Lanthanide tetrad effect in the Ln3+ ionic radii and refined spin-pairing energy theory

1992

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The refined spin-pairing energy theory (RSPET) has been improved in order to understand quan titatively the tetrad or double-double effects recognized in the Ln3+ ionic radii. Since the ionic radii have been determined from the lattice constants and structural parameters of Ln01.5 and LnF3, the lattice energies of the compounds and the enthalpy difference of d Hf (LnF3)-A Hf (LnO1,5) have been exam ined by the improved RSPET. The RSPET parameters for the lowest levels of 4fq electronic configura tions strongly depend upon the effective nuclear charge (Z*). Such effects due to Z* have been taken into account. This made it possible to separate the variations in the lattice energies and the enthalpy difference across the Ln3+ series into the following two parts: (1) the large variation as a smooth func tion of q (the lanthanide contraction trend), and (2) the small zig-zag variation referred to the tetrad or double-double effect. The lattice energy of Ln01.5 and A Hf (LnF3)-A Hf (Ln01.5) exhibit upward con cave tetrad curves in their plots against q of Ln3+. The tetrad effect in the lattice energy of LnF3 is less conspicuous. This means that the Racah parameters for Ln3+ decrease very slightly in going from the gaseous free Ln3+ to LnF3, and then decrease greatly to Ln01.5, in accordance with the nephelauxetic series. The differences in Racah parameters between LnF3 and Ln01,5 have been estimated from A Hf(LnF3) -A Hf(Ln01.5) by means of an inversion technique based on the improved RSPET. The RSPET results for the thermochemical data are consistent with the careful spectroscopic determinations of Racah parameters for NdF3 and Nd01.5. Both the tetrad effect and the smooth lanthanide contraction seen in the Ln3+ ionic radii can be interpreted in terms of the quantum mechanical energetics of 4f elec trons.

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Section: Screening Constant and A New Rspet Formulationsupporting

confidence: 50%

Lanthanide tetrad effect in the Ln3+ ionic radii and refined spin-pairing energy theory

1992

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“…Among the major causes of such problems, the authors name large number of adjustable parameters used in fittings and the dependence of the optimized sets on the chosen starting CFP values. Several methods to obtain the starting CFP values were outlined in [18], e.g., ab initio calculations, "descent of symmetry" method, and Antic-Fidancev et al [58] method. The method [58] yields alternative correlated CFP sets of different origin than those outlined in section 2 and hence is discussed in section 4.7.1.…”

Section: Fitting Procedures and Meaning Of Fitted Crystal Field Param...mentioning

confidence: 99%

“…Several methods to obtain the starting CFP values were outlined in [18], e.g., ab initio calculations, "descent of symmetry" method, and Antic-Fidancev et al [58] method. The method [58] yields alternative correlated CFP sets of different origin than those outlined in section 2 and hence is discussed in section 4.7.1. Other factors that influence the optimized CFP sets are also discussed in [18], e.g., truncation of the basis sets by arbitrarily omitting certain energy levels, usage by various research groups of different levels for a particular transition ion in the fitting procedure, or different experimental methods used to obtain the spectroscopic data.…”

Section: Fitting Procedures and Meaning Of Fitted Crystal Field Param...mentioning

confidence: 99%

Intrinsically incompatible crystal (ligand) field parameter sets for transition ions at orthorhombic and lower symmetry sites in crystals and their implications

Rudowicz¹,

Gnutek²

2010

Physica B: Condensed Matter

119

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“…However, strong spin-orbit coupling of the 4f electrons breaks the LS-scheme of the energy levels of the Gd 3+ ion and mixes the 8 S 7/2 and 6 P 7/2 states. 10 Since the ground-state multiplet contains an admixture of the L = 0 states, it can be split by the crystal field. Crystal-field splitting of the order of 0.8 K was observed for Gd 3+ ions in yttrium-gallium garnet.…”

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confidence: 99%

Single-ion anisotropy in the gadolinium pyrochlores studied by electron paramagnetic resonance

et al. 2005

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The electron paramagnetic resonance is used to measure the single-ion anisotropy of Gd 3+ ions in the pyrochlore structure of (Y1−xGdx)2Ti2O7 . A rather strong easy-plane type anisotropy is found. The anisotropy constant D is comparable to the exchange integral J in the prototype Gd2Ti2O7, D ≃ 0.75J, and exceeds the dipolar energy scale. Physical implications of an easy-plane anisotropy for a pyrochlore antiferromagnet are considered. We calculate the magnetization curves at T = 0 and discuss phase transitions in magnetic field.PACS numbers: 76.30. Kg, 75.50.Ee, 75.10.Hk Pyrochlore antiferromagnets have been actively studied in the past due to their unusual properties. 1 The magnetic ions in these compounds form a network of corner-sharing tetrahedra, which is prone to a high degree of geometric frustration. The ground state of a classical Heisenberg antiferromagnet on a pyrochlore lattice is macroscopically degenerate and remains disordered. 2 Since weaker residual interactions are always present in real magnetic materials, an important question is about a separation of energy scales. The corresponding knowledge helps to clarify how the macroscopic entropy freezes as T → 0 and what type of magnetically ordered, spinliquid, or glassy state is eventually stabilized.Gadolinium pyrochlores Gd 2 Ti 2 O 7 and Gd 2 Sn 2 O 7 are considered to be the best realizations of the Heisenberg model on a pyrochlore lattice, since Gd 3+ is, nominally, in a 8 S 7/2 state with completely frozen orbital degrees of freedom. Both compounds order at temperatures of about 1 K, 3,4,5 while Gd 2 Ti 2 O 7 exhibits also multiple phases in magnetic field. 4,6 This has been attributed to weaker dipolar interactions between the S = 7/2 gadolinium spins, 3,7,8 though no unambiguous explanation neither of the phase diagram of Gd 2 Ti 2 O 7 nor of the neutron-diffraction measurements 9 has been presented.Single-ion effects have so far been neglected for the two gadolinium pyrochlores. However, strong spin-orbit coupling of the 4f electrons breaks the LS-scheme of the energy levels of the Gd 3+ ion and mixes the 8 S 7/2 and 6 P 7/2 states. 10 Since the ground-state multiplet contains an admixture of the L = 0 states, it can be split by the crystal field. Crystal-field splitting of the order of 0.8 K was observed for Gd 3+ ions in yttrium-gallium garnet. 11 The amplitude of such a splitting is comparable to the exchange coupling and the dipolar energy in the prototype Gd 3 Ga 5 O 12 . Thus, an accurate study of the single-ion anisotropy in the Gd-based pyrochlores is necessary to understand the magnetic properties of these materials.To study properties of isolated Gd 3+ ions we have prepared single-crystals of non-magnetic Y 2 Ti 2 O 7 diluted with a small amount (nominally 0.5%) of Gd. The crystals were grown by traveling solvent floating zone technique. After growth the oriented single-crystals were annealed in an oxygen atmosphere. The absence of parasitic phases has been verified by powder X-ray diffraction. The magnetization of the referen...

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Crystal-field splittings of gadolinium (4f7) levels in C-type rare earth oxides

Cited by 36 publications

References 14 publications

Lanthanide tetrad effect in the Ln3+ ionic radii and refined spin-pairing energy theory

Lanthanide tetrad effect in the Ln3+ ionic radii and refined spin-pairing energy theory

Intrinsically incompatible crystal (ligand) field parameter sets for transition ions at orthorhombic and lower symmetry sites in crystals and their implications

Single-ion anisotropy in the gadolinium pyrochlores studied by electron paramagnetic resonance

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