Thermoelectric power of cerium and ytterbium intermetallics

Zlatič, V.; Horvatić, B.; Milat, I.; Coqblin, B.; Czycholl, Gerd; Grenzebach, Claas

doi:10.1103/physrevb.68.104432

Cited by 102 publications

(98 citation statements)

References 68 publications

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“…16 but the hightemperature data of our samples is seen to follow the generally expected behavior within the framework of the Coqblin-Schrieffer model 17,18,19 , and the disorder-related effects discussed here. For the unannealed samples, the response should be a combination of a low T K Kondo lattice and single-Yb "impurity" effects with high T K values, both of which are known to greatly increase the absolute values of S(T ) for T ≫ T K .…”

supporting

confidence: 68%

Drastic annealing effects in transport properties of single crystals of theYbNi2B2Cheavy fermion system

Ávila

Bud’ko²,

Canfield³

2002

Phys. Rev. B

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We report temperature dependent resistivity, specific heat, magnetic susceptibility and thermoelectric power measurements made on the heavy fermion system YbNi2B2C, for both as grown and annealed single crystals. Our results demonstrate a significant variation in the temperature dependent electrical resistivity and thermoelectric power between as grown crystals and crystals that have undergone optimal (150 hour, 950• C) annealing, whereas the thermodynamic properties: (cp(T ) and χ(T )) remain almost unchanged. We interpret these results in terms of redistributions of local Kondo temperatures associated with ligandal disorder for a small (∼ 1%) fraction of the Yb sites.PACS numbers: 74.70. Dd,75.30.Mb,72.15.Qm Among the rich variety of physical phenomena displayed by the RNi 2 B 2 C nickel boro-carbide family 1,2,3,4 , YbNi 2 B 2 C (Yb-1221) is unique so far in its behavior as a heavy fermion system 5,6 with an electronic specific heat coefficient, γ ≈ 500mJ/molK 2 , and a Kondo temperature, T K ≈ 10K: a temperature scale that is conveniently isolated from other characteristic temperatures such as superconducting or magnetic condensates (T c , T N < 0.03K, if they exist at all), and crystal electric field splitting (T cef ≈ 100K) 7,8 . The heavy fermion behavior is understood as a consequence of the fact that the ytterbium 4f levels easily hybridize with the electronic conduction band levels near the Fermi surface. Such heavy electron systems often display many unusual physical properties 9 , one common example being disorderrelated variation in the behavior of different samples of the same compound 9,10 .Recently the effects of annealing on the electrical resistivity of R-1221 single crystals (R = Y, Gd-Lu) were studied 11 , and once again Yb-1221 showed anomalous properties in comparison to other members of the series. Whereas annealing of crystals with R = Y, Lu, Tm-Gd simply leads only to changes in the residual resistivity, radical changes in R(T ) behavior were observed for Yb-1221 over the full (2K − 300K) temperature range. The change in R(T ) was so dramatic that comparison of normalized resistance curves R(T )/R(300) became highly questionable.To overcome this problem and better understand what is happening to the Yb-1221 crystals as they go through annealing processes, in the present work careful resistivity measurements were made on Yb-1221 crystals cut into well-defined geometries, such that no normalization is necessary and direct comparison of ρ(T ) for different samples and annealing procedures is possible. The results, in combination with measurements of specific heat, magnetic susceptibility and thermoelectric power, allow us to propose a mechanism in which optimal annealing is essentially affecting the ligandal disorder associated with a small fraction (∼ 1%) of the Yb sites. But given that Yb is a hybridizing rare earth ion, it is far more sensitive to such disorder than its non-hybridizing neighbors. Yb-1221 then presents a model heavy fermion system that allows for the study of how small...

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supporting

confidence: 68%

Drastic annealing effects in transport properties of single crystals of theYbNi2B2Cheavy fermion system

Ávila

Bud’ko²,

Canfield³

2002

Phys. Rev. B

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“…In the paramagnetic region, the overall behavior of the thermopower of Ce 2 RhSi 3 is similar to that reported for Ce-based Kondo lattices, e.g. CeAl 3 , CePdSn, CePdGe, or CePtGe, and classified as "type (b)" being explainable in the framework of the Coqblin-Schrieffer model [8].…”

Section: Methodssupporting

confidence: 60%

“…In the paramagnetic region the temperature dependences of the Seebeck coefficient measured along the main crystallographic axes can be effectively described by a phenomenological model which takes into account scattering processes of the conduction electrons from a broad s-d band into a narrow 4f quasiparticle band. The overall shape of the temperature variations of the thermopower of Ce 2 RhSi 3 is similar to that typical of dense Kondo systems, and hence it is tempting to apply to this compound a more sophisticated theoretical approach based on the Coqblin-Schrieffer model that takes into account crystal field interactions as well as spin and valence fluctuations [8,14]. This issue will be addressed in our forthcoming paper.…”

Section: Resultsmentioning

confidence: 99%

Thermoelectric Power of Single-Crystalline Ce₂RhSi₃

et al. 2009

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High-quality single crystal of Ce 2 RhSi 3 was studied by means of thermoelectric power measurements carried out down to 2 K in external magnetic fields up to 13 T. The results obtained above 50 K were interpreted in terms of a modified two-band model that takes into account temperature variation of the width of 4f -derived narrow band located near the Fermi level. At lower temperatures the thermopower exhibits more complex temperature dependences that likely involve interplays of magnetic exchange, Kondo and crystal-field interactions.

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“…6. Even if a generic behavior is absent in the thermoelectric response of HF materials, it seems to be more or less characteristic [54][55][56] for Ce compounds close to the magnetic instability that at low T a negative contribution competes with the more ordinary positive contribution (related to the T K and T CEF energy scales) to S. Hence, a reduction of this negative component is expected when p is applied, since an increasing hybridization generally favors the nonmagnetic FIG. 12. (Color online) T dependence of the Nernst signal N (8 T) at several p up to 6.8 GPa.…”

Section: Transverse Resistivity: Hall Effectmentioning

confidence: 99%

Heavy fermion superconductor CeCu2Si2under high pressure: Multiprobing the valence crossover

Seyfarth

Rüetschi²,

Sengupta³

et al. 2012

Phys. Rev. B

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The first heavy fermion superconductor CeCu 2 Si 2 has not revealed all its striking mysteries yet. At high pressures, superconductivity is supposed to be mediated by valence fluctuations, in contrast to ambient pressure, where spin fluctuations most likely act as pairing glue. We have carried out a multiprobe (electric transport, thermopower, ac specific heat, Hall and Nernst effects) experiment up to 7 GPa on a high-quality CeCu 2 Si 2 single crystal. For the first time, the resistivity data make it possible quantitatively to draw the valence crossover line within the p-T plane and to locate the critical end point at 4.5 ± 0.2 GPa and a slightly negative temperature. In the same pressure region, remarkable features have also been detected in the other physical properties, presumably acting as further signatures of the Ce valence crossover and the associated critical fluctuations: We observe maxima in the Hall and Nernst effects and a sign change and a strong sensitivity on magnetic field in the thermopower signal.

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Thermoelectric power of cerium and ytterbium intermetallics

Cited by 102 publications

References 68 publications

Drastic annealing effects in transport properties of single crystals of theYbNi2B2Cheavy fermion system

Drastic annealing effects in transport properties of single crystals of theYbNi2B2Cheavy fermion system

Thermoelectric Power of Single-Crystalline Ce₂RhSi₃

Heavy fermion superconductor CeCu2Si2under high pressure: Multiprobing the valence crossover

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Thermoelectric power of cerium and ytterbium intermetallics

Cited by 102 publications

References 68 publications

Drastic annealing effects in transport properties of single crystals of theYbNi2B2Cheavy fermion system

Drastic annealing effects in transport properties of single crystals of theYbNi2B2Cheavy fermion system

Thermoelectric Power of Single-Crystalline Ce2RhSi3

Heavy fermion superconductor CeCu2Si2under high pressure: Multiprobing the valence crossover

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Product

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Thermoelectric Power of Single-Crystalline Ce₂RhSi₃