Kondo lattice behavior observed in the CeCu9In2 compound

Abstract

We report systematic studies of CeCu 9 In 2 , which appears to be a new Kondo lattice system. Electrical resistivity exhibits a logarithmic law characteristic of Kondo systems with a broad maximum at T coh ≈45 K and it obeys the Fermi liquid theory at low temperature. Specific heat of CeCu 9 In 2 is well described by the Einstein and Debye models with electronic part at high temperature. Fitting of the Schottky formula to low temperature 4f contribution to specific heat yielded crystal field splitting of 50.2 K between a doublet and quasi-quartet. The Schotte-Schotte model estimates roughly Kondo temperature as T K ≈5 K, but does not reproduce well the data due to a sharp peak at 1.6 K. This structure should be attributed to a phase transition, a nature of which is possibly antiferromagnetic. Specific heat is characterized with increased Sommerfeld coefficient estimated as γ ≈132 mJ/(mole·K 2 ). Spectra of the valence band, which have been collected with ultraviolet photoelectron spectroscopy (UPS), show a peak at binding energy≈250 meV, which originates from the Ce 4f electrons and is related to the 4f 1 7/2 final state. Extracted 4f contribution to the spectral function exhibits also the enhancement of intensity in the vicinity of the Fermi level. Satellite structure of the Ce 3d levels spectra measured by X-ray photoelectron spectroscopy (XPS) has been analyzed within the framework of the Gunnarsson-Schönhammer theory. Theoretical calculations based on density functional theory (FPLO method with LDA+U approach) delivered densities of states, band structures and Fermi surfaces for CeCu 9 In 2 and LaCu 9 In 2 . The results indicate that Fermi surface nesting takes place in CeCu 9 In 2 .

Luminescence and Energy Transfer of Color-Tunable Y2Mg2Al2Si2O12:Eu2+,Ce3+ Phosphors

“…42 The binding energies at 906.8 and 885.5 eV are attributed to Ce 3d 3/2 and Ce 3d 5/2 , respectively. 43 For the crystal structure, as we previously reported, 36 these are six cation sites in the YMAS host, including S1. It can be found that these parameters (a, b, c, and V) show an increasing trend with the doping of Eu 2+ and Ce 3+ .…”

“…The binding energies at 50.1, 74.2, and 102.1 eV are related to Mg 2p, Al 2p, and Si 2p, respectively. , The Eu 3d spectra are composed of two peaks at 1158.3 and 1123.9 eV, ascribed to Eu 3d 3/2 and Eu 3d 5/2 of Eu 2+ , respectively . The binding energies at 906.8 and 885.5 eV are attributed to Ce 3d 3/2 and Ce 3d 5/2 , respectively . For the crystal structure, as we previously reported, these are six cation sites in the YMAS host, including Y and Mg1 (CN = 8, where CN stands for the coordination number), Mg2 and Al1 (CN = 6) and Al2 and Si (CN = 4).…”

A Canonical Transformation for the Anderson Lattice Hamiltonian with f–f Electron Coupling

“…When rare-earth or actinide atoms constitute a sublattice in a compound, the system may be called Kondo lattice compound. The examples may include CeAl 3 [8][9][10], CeCu 2 Si 2 [11][12][13], UBe 13 [14][15][16], CeB 6 [17,18], CeCu 6 [19][20][21], CePtSi [22], Ce 2 PdIn 8 [23], CeGe [24], (Ce 1−x La x )Cu 2 Ge 2 [25], Yb 3 Ru 4 Al 12 [26], UAuBi 2 [27], Ce(Cu, Al,Si) 2 [28], CeCu 2 Mg [29], Ce 2 Rh 3 Sn 5 [30], CeRhIn 5 [31], CeCu 9 In 2 [32], and others. Doniach [33] studied a one-dimensional Kondo lattice model for Kondo lattice compound and suggested that a second-order transition from an antiferromagnetic state to a Kondo spin compensated ground state could occur as the exchange coupling constant J increased to a critical value J c ; for systems in which J ∼ J c , a very weak sublattice magnetization may occur as a result of nearly complete spin-compensation.…”