Specific heat of a Coqblin-Schrieffer model with crystal fields: New crossover features and scaling properties

Desgranges, H.-U.; Rasul, J.W.

doi:10.1103/physrevb.32.6100

Cited by 53 publications

(35 citation statements)

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“…If we consider the degenerate 4 f -electron state with the J-multiplet of 5/2, the calculation tentatively explains the peak structure of the C m semi-quantitatively by selecting a considerably high T K = 600 K. 13) In order to confirm the validity of the result, we need the calculation considering properly the real situation which must be much complicated. 14) On the other hand, interestingly, we recognize an additional broad peak centering at 30 K for x = 0.3, and it appears also for x = 0.4. It does not apparently relate to the above mentioned hump and peak due to the Kondo effect, since the T K is expected to increase monotonically from 30 K with increasing x = 0 up to 1.…”

Section: Resultsmentioning

confidence: 93%

Anomalous Behavior on Specific Heat and Thermoelectric Power in Wide Range of Temperatures in CeNi₂(Ge_1-xSi_x)₂

et al. 2011

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We present magnetic specific heat C m and thermoelectric power S for CeNi 2 (Ge 1−x Si x ) 2 (x = 0 ∼ 0.4) in a wide range of temperatures above 1 K to 300 K. Both C m and S show a characteristic broad peak around 100 ∼ 150 K due to the Kondo effect with high Kondo temperature which is comparable to the crystalline electric field. On the other hand, C m /T and S /T synchronously increase logarithmically at low temperatures on cooling for all x investigated. The anomalous temperature dependence both in C m /T and S /T at low temperatures is interpreted as non-Fermi-liquid behavior due to the proximity to the quantum critical point for x ≤ 0.1, and due to Kondo disorder for x ≥ 0.3.

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Section: Resultsmentioning

confidence: 93%

Anomalous Behavior on Specific Heat and Thermoelectric Power in Wide Range of Temperatures in CeNi₂(Ge_1-xSi_x)₂

et al. 2011

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confidence: 85%

“…The thermodynamic properties of the single-impurity model have been calculated exactly using the Betheansatz technique, 14,15,16,17,18 and also approximately within the Non-Crossing Approximation (NCA), which shows good agreement with the former. 19 However, to the best of our knowledge, it has always been assumed that the hybridization V m between any state of the magnetic configuration |m and the conduction electrons is independent of m even when the CEF is included.…”

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confidence: 85%

“…19 However, to the best of our knowledge, it has always been assumed that the hybridization V m between any state of the magnetic configuration |m and the conduction electrons is independent of m even when the CEF is included. 14,15,16 This is a requirement for the integrability of the problem; 20 although, there is no symmetry requirement to have the same V m for each orbital in the presence of a CEF. The different orientations of the orbitals relative to the nearest-neighbor atoms clearly indicate that the hybridizations must be a function of m. It is essential to consider this effect in order to explain the magnetic susceptibility χ(T ) measurements of Yb 2 M 3 Ga 9 (M= Rh, Ir) shown here as well as various other experimental observations in related materials.…”

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Crystal-field effects in the mixed-valence compoundsYb2M3Ga9(M=

et al. 2005

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Magnetic susceptibility, heat capacity, and electrical resistivity measurements have been carried out on single crystals of the intermediate valence compounds Yb2Rh3Ga9 and Yb2Ir3Ga9. These measurements reveal a large anisotropy due apparently to an interplay between crystalline electric field (CEF) and Kondo effects. The temperature dependence of magnetic susceptibility can be modelled using the Anderson impurity model including CEF within an approach based on the NonCrossing Approximation.PACS numbers: 75.30.Mb,75.20.Hr,71.27.+a,71.28.+d The intermediate valence compounds pose one of the most challenging problems of strongly correlated electron systems. Different ingredients contribute to the complexity of these fascinating systems: the presence of strong Kondo interactions, the level structure of the crystal electric field (CEF) f -orbitals, the different hybridizations between each level and the conduction band, and the eventual coherence effects and magnetic interactions introduced by the periodicity of the Kondo lattice. 1Strong valence fluctuations are observed in the intermetallic compounds with Ce, Yb and U. In particular, Yb compounds attract a great deal of interest because the trivalent Yb ion is at least in some sense the hole counterpart of the Ce 3+ ion which has one electron in its 4f shell. As in the case of the Ce compounds, 2 the Ybbased intermetallics exhibit a diversity of physical properties that remain to be understood. 3The isostructural series of compounds R 2 M 3 X 9 (R = La, Ce, Yb, U; M=Co, Rh, Ir; X = Al, Ga) exhibit antiferromagnetic ordering for R=Yb, X=Al, and mixedvalence behavior for R=Ce,Yb and X=Ga. 4,5,6,7 All the U-based compounds order antiferromagnetically at temperatures below 40 K.4 The Yb 2 M 3 Ga 9 compounds are a suitable class of materials for studying the difference in the electronic structure between the magnetically ordered Kondo lattice and the mixed-valence systems. The orientation-dependent temperature T max of the maximum in the magnetic susceptibility suggests the possibility of an anisotropic Kondo effect.8,9 Previously, Petrovic et al. studied ternary R-Ir-Ga compounds (R=rare earth) that were assigned the RIr 2 Ga stoichiometry in their work. 10,11,12 Elemental analysis studies unavailable to these previous authors suggest that R 2 Ir 3 Ga 9 is the correct stoichiometry of these materials instead. The R 2 Ir 3 Ga 9 compounds with Ce and Yb show reduced magnetic moments and the absence of magnetic order above 0.04 K. 11The thermodynamic properties of the single-impurity model have been calculated exactly using the Betheansatz technique, 14,15,16,17,18 and also approximately within the Non-Crossing Approximation (NCA), which shows good agreement with the former.19 However, to the best of our knowledge, it has always been assumed that the hybridization V m between any state of the magnetic configuration |m and the conduction electrons is independent of m even when the CEF is included.14,15,16 This is a requirement for the integrability of the problem; 20 a...

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“…A similar scenario is observed in Ce(Pd 1−z Ni z ) 2 Al 3 , which becomes NM at high Ni concentration. 32) Although in these systems T N practically does not depend on con- 38) centration, T N = f (z), the entropy gain up to that temperature decreases due to the increase of T K (z), as shown in Fig. 12(b).…”

Section: )mentioning

confidence: 86%

Thermodynamical Analysis of the Magnetic Phase Diagrams of Ce Systems

Sereni

2001

J. Phys. Soc. Jpn.

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Three types of magnetic phase diagrams as a function of composition or pressure, f (z, p), are identified among Ce systems: I) with the ordering temperature T ord → 0 monotonously, followed by a narrow region where non-Fermi-liquid (NFL) behavior is observed; II) with T ord vanishing at finite temperature, but followed by an extended NFL region, and III) where T ord remains nearly constant. Among the analyzed systems intrinsic differences are found in the evolution of their respective properties, namely: in group-I an increase of the density of excitations is observed below T ord . In group-II the evanescense of T ord (z, p) coincides with the extrapolation to zero of the magnetic free energy (ΔG → 0), and the existence of a reference function implying that T K = f (z, p), whereas T ord = f (z, p). Finally, group-III is also characterized by the evanescense of T ord where ΔG → 0, but in this case T ord = f (z, p) whereas T K = f (z, p). The characteristics of each group are discussed and compared together with the different C p (T )/T dependencies at T ≥ T ord and some related scalings, which allow to recognize a quasi-paramagnetic phase.

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Specific heat of a Coqblin-Schrieffer model with crystal fields: New crossover features and scaling properties

Cited by 53 publications

References 15 publications

Anomalous Behavior on Specific Heat and Thermoelectric Power in Wide Range of Temperatures in CeNi₂(Ge_1-xSi_x)₂

Anomalous Behavior on Specific Heat and Thermoelectric Power in Wide Range of Temperatures in CeNi₂(Ge_1-xSi_x)₂

Crystal-field effects in the mixed-valence compoundsYb2M3Ga9(M=

Thermodynamical Analysis of the Magnetic Phase Diagrams of Ce Systems

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Specific heat of a Coqblin-Schrieffer model with crystal fields: New crossover features and scaling properties

Cited by 53 publications

References 15 publications

Anomalous Behavior on Specific Heat and Thermoelectric Power in Wide Range of Temperatures in CeNi2(Ge1-xSix)2

Anomalous Behavior on Specific Heat and Thermoelectric Power in Wide Range of Temperatures in CeNi2(Ge1-xSix)2

Crystal-field effects in the mixed-valence compoundsYb2M3Ga9(M=

Thermodynamical Analysis of the Magnetic Phase Diagrams of Ce Systems

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Anomalous Behavior on Specific Heat and Thermoelectric Power in Wide Range of Temperatures in CeNi₂(Ge_1-xSi_x)₂

Anomalous Behavior on Specific Heat and Thermoelectric Power in Wide Range of Temperatures in CeNi₂(Ge_1-xSi_x)₂