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Abstract: In this paper, the IR absorption spectra of YbMnO3 are reported as a function of temperature. In addition to the wide and strong charge transfer band due to manganese in visible, the absorption spectra include sharp lines characteristic for the 2F7/2 → 2F5/2 transition of Yb3+ at around 10000cm−1. The number of lines exceeds the theoretical one for the two Yb3+ sites with C 3 (two third) and C 3v (one third of the sites) point symmetries. Magnetic ordering of the manganese sublattice below T N at ∼75K creates a molecular field that splits the Kramers doublets of the Yb3+ ions in the C 3 site. The splitting varies (at 5K) from a few up to 30cm−1. Despite accounting for this splitting, the number of lines is still too high due to the vibronic coupling. The parameters of the crystal field acting at the Yb3+ sites were predicted using the ab initio methods and the superposition model calculations considering the available structural data. A rather good agreement was obtained with the observed splitting of the 2F7/2 and 2F5/2 manifolds. [Copyright &y& Elsevier]

Abstract: First-principles calculations based on density-functional theory (DFT) were performed on RPt3Si (R=Pr, Nd, Sm) for the first time. The electronic density of states (DOS) and bonding properties were studied using relativistic full-potential APW plus local orbitals calculations. The crystal-field (CF) splitting was derived for NdPt3Si and SmPt3Si by fitting the temperature-dependent magnetic susceptibility. The starting estimate of the CF parameters for fitting procedure was obtained from first-principles calculations based on DFT. [Copyright &y& Elsevier]

Abstract: A computational model for the calculation of the bulk magnetic properties of rare-earth ferrimagnets and antiferromagnets was developed and justified theoretically in the framework of mean-field theory. To demonstrate its utility, the model was applied to calculate the anisotropic Heisenberg exchange constants of CeTe2 by fitting magnetization curves numerically, and to derive analytical expressions for the spontaneous magnetization as well as the Neél temperature by considering only the crystal-field (CF) ground-state doublet. It turns out that the temperature dependencies of the magnetization and the specific heat calculated with the formulas in absence of an external field are identical with the plots obtained directly with the full lowest CF J-multiplet, manifesting the strong role of the Kramers doublet in the magnetic process at low temperatures. Finally, the model was applied to investigate the effects of the quadrupolar and magneto-elastic (QM) interactions on the magnetic properties of the system. [Copyright &y& Elsevier]

• Magnetic susceptibility and specific heat of polycrystalline Dy2Ir2O7 are analysed within the frame of mean field approximation considering model of crystal field and Zeeman interaction. • The Ir-Ir correlations are captured as bifurcation of ZFC/FC magnetic susceptibilities at 128 K and anomaly in specific heat at respective temperature. • The deviation from mean-field behaviour of Dy ions is deduced from the magnetic susceptibility and also isothermal magnetization data, where the calculations cannot explain the magnetic behaviour already well above the temperature of Dy-Dy correlations (1 K). • The anomaly in magnetic contribution to specific heat was identified at 20 K indicating the possible presence of strong Ir-Dy correlations. The magnetic properties of pyrochlore iridate Dy 2 Ir 2 O 7 prepared by CsCl flux method were investigated by means of heat capacity and magnetization measurements. The low temperature behaviour was confirmed to be consistent with previously published results, whereas the high temperature data and their analysis are presented for the first time. The bifurcation of zero field-cooled and field-cooled magnetization curves coincides well with the onset of the anomaly in specific heat pointing to an ordering of the iridium sublattice. We confront the previously determined Dy3+ CF scheme with our high-temperature magnetization and specific heat data. The difference between calculations and experimental data, represented by 20 K specific heat anomaly, suggests the behaviour beyond the mean field approximation. The Dy 2 Ir 2 O 7 differs from the rest of the heavy rare-earth pyrochlore iridates, where the mean field approximation constitutes an adequate description. The deeper understanding of the Dy 2 Ir 2 O 7 magnetic behaviour requires, among others, also the phonon spectra studies. [ABSTRACT FROM AUTHOR]

Abstract: A new method for calculations of crystal field (CF) interaction in alloys containing rare earths (4f electron CF) has been developed. The method is based on density-functional theory (DFT) and uses the full-potential local-orbitals (FPLO) method combined with the coherent-potential approximation (CPA). The method is successfully applied to calculate the CF interaction in RENi4Al alloys. [Copyright &y& Elsevier]

In this work, we report results of specific heat and magnetization measurements on a single crystal of Nd 2 IrIn 8 . The compound orders antiferromagnetically below the Néel temperature of 12.5(2) K. Nd 2 IrIn 8 exhibits magnetic anisotropy with c as the easy axis. Two sharp metamagnetic transitions are present at 2 K. The measured data have been used to construct the low-temperature phase diagram for H || c . The measured susceptibilities and specific heat are compared to results based on first-principles calculations of the crystal-field parameters. [ABSTRACT FROM AUTHOR]

We present the study of the Kondo antiferromagnet CePtSn, whose magnetic properties at T>TN can be explained by a strong anisotropy of the crystal-field (CF) potential on the Ce sites, which have an orthorhombic point-group symmetry. Applying a microscopic model with parameters deduced from magnetization and inelastic neutron scattering (INS) data, we predict a strong magnetic dipole moment parallel to the a-axis in the ground state. The dramatically increased count rate at the upgraded ILL three-axis spectrometer IN20 permits now to use the polarized beam even with a small single crystal sample (0.2 cm3) to separate the CF signal from phonon background and to employ the XYZ polarization analysis to confirm directly this previously deduced anisotropy of the local CF Hamiltonian. [Copyright &y& Elsevier]