Intersite Coupling Effects in a Kondo Lattice (original) (raw)
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Dilution and non-Fermi-liquid effects in the CePtIn Kondo lattice
Journal of Physics: …, 2009
Measurements of electrical resistivity ((T)), magnetoresistivity (MR), magnetic susceptibility ((T)) and heat capacity (C P (T)) are presented for the (Ce 1x La x )PtIn alloy system of which the CePtIn parent is a known dense Kondo compound that does not order magnetically down to 50 mK. (T) for alloys 0 x 0.8 exhibits CurieWeiss behaviour. (T) results indicate a transition from a dense Kondo behaviour for 0 x 0.2 to a singleion Kondo region (0.3 x 0.8). The Kondo energy scale as given by T K values calculated from MR studies and by the temperature ρ(mag) max T where the magnetic contribution to (T) exhibits a maximum value, is compared with theoretical models. It is shown that the experimental results not only depend on a volume effect as given by the compressible Kondo lattice model of Lavagna but in addition confirm the more complex behaviour recently presented by Burdin and Fulde for a Kondo alloy system in which the magnetic (Ce) and non-magnetic (La) atoms are distributed randomly. NonFermiliquid behaviour is predicted by Burdin and Fulde at certain critical concentrations of the alloy system and experimental evidence for this is presented through (T), (T) and C P (T) measurements.
Metallic ferromagnetism in the Kondo lattice
Proceedings of the National Academy of Sciences, 2010
Metallic magnetism is both ancient and modern, occurring in such familiar settings as the lodestone in compass needles and the hard drive in computers. Surprisingly, a rigorous theoretical basis for metallic ferromagnetism is still largely missing. The Stoner approach perturbatively treats Coulomb interactions when the latter need to be large, whereas the Nagaoka approach incorporates thermodynamically negligible holes into a half-filled band. Here, we show that the ferromagnetic order of the Kondo lattice is amenable to an asymptotically exact analysis over a range of interaction parameters. In this ferromagnetic phase, the conduction electrons and local moments are strongly coupled but the Fermi surface does not enclose the latter (i.e., it is “small”). Moreover, non-Fermi-liquid behavior appears over a range of frequencies and temperatures. Our results provide the basis to understand some long-standing puzzles in the ferromagnetic heavy fermion metals, and raise the prospect for ...
Strange-metal behaviour in a pure ferromagnetic Kondo lattice
Nature, 2020
The strange metal phases found to develop in a wide range of materials near a quantum critical point (QCP), have posed a long-standing mystery. The frequent association of strange metals with unconventional superconductivity and antiferromagnetic QCPs [1-4] has led to a belief that they are highly entangled quantum states [5]. Ferromagnets, by contrast are regarded as an unlikely setting for strange metals, for they are weakly entangled and their QCPs are often interrupted by competing phases or first order phase transitions [6-8]. Here, we provide compelling evidence that the stoichiometric heavy fermion ferromagnet CeRh 6 Ge 4 [9, 10] becomes a strange metal at a pressure-induced QCP: specific heat and resistivity measurements demonstrate that the FM transition is continuously suppressed to zero temperature revealing a strange metal phase. We argue that strong magnetic anisotropy plays a key role in this process, injecting entanglement, in the form of triplet resonating valence bonds (tRVBs) into the ordered ferromagnet. We show that the singular transformation from tRVBs into Kondo singlets that occurs at the QCP causes a jump in the Fermi surface volume: a key driver of strange metallic behavior. Our results open up a new direction for research into FM quantum criticality, while also establishing an important new setting for the strange metal problem. Most importantly, strange metallic behavior at a FM quantum critical point suggests that it is quantum entanglement rather than the destruction of antiferromagnetism that is the common driver of the many varied examples of strange metallic behavior. Quantum materials augmented by strong electronic correlations are promising for applications, but the electronic interactions that empower these materials challenge our understanding. One of the most pressing questions in strongly correlated electronic systems is the origin of the strange metallic behavior which develops at a quantum critical phase transition between a delocalized Fermi liquid (FL), and a localized or partially localized electronic phase. A prime example is the strange metal (SM) phase which develops in the normal state of cuprate superconductors at optimal doping, characterized by a robust linear resistivity and a logarithmic temperature dependence of the specific heat coefficient [2, 3]; similar be
Coexistence of magnetic order and valence fluctuations in the Kondo lattice system<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML">mml:mrowmml:msubmml:miCemml:mn2mml:msubmml:miRhmml:mn3mml:msubmml:miSn<mm...
Physical review, 2017
We report on the electronic band structure, structural, magnetic and thermal properties of Ce2Rh3Sn5. Ce LIII-edge XAS spectra give direct evidence for an intermediate valence behaviour. Thermodynamic measurements reveal magnetic transitions at TN1 ≈ 2.9 K and TN2 ≈ 2.4 K. Electrical resistivity shows behaviour typical for Kondo lattices. The coexistence of magnetic order and valence fluctuations in a Kondo lattice system we attribute to a peculiar crystal structure in which Ce ions occupy two distinct lattice sites. Analysis of the structural features of Ce2Rh3Sn5, together with results of electronic band structure calculations, thermodynamic and spectroscopic data indicate that at low temperatures only Ce ions from the Ce1 sublattice adopt a stable trivalent electronic configuration and show local magnetic moments that give rise to the magnetic ordering. By contrast, our study suggests that Ce2 ions exhibit a nonmagnetic Kondo-singlet ground state. Furthermore, the valence of Ce2 ions estimated from the Ce LIII-edge XAS spectra varies between +3.18 at 6 K and +3.08 at room temperature. Thus, our joined experimental and theoretical investigations classify Ce2Rh3Sn5 as a multivalent charge-ordered system.
The non-Fermi-liquid behavior in magnetic Kondo lattices induced by peculiarities of spin dynamics
Physics Letters A, 2000
A scaling consideration of the Kondo lattices is performed with account of singularities in the spin excitation spectral Ž . function. It is shown that a non-Fermi-liquid NFL behaviour occurs naturally for complicated magnetic structures with several magnon branches. This may explain the fact that a NFL behaviour often takes place in the heavy-fermion systems with peculiar spin dynamics. The mechanisms proposed lead to some predictions about behaviour of specific heat, resistivity, magnetic susceptibility and anisotropy parameter, which can be verified experimentally. q 2000 Published by Elsevier Science B.V. All rights reserved. PACS: 75.30.Mb; 71.28 0375-9601r00r$ -see front matter q 2000 Published by Elsevier Science B.V. All rights reserved.
Physical Review B, 2010
We report measurements of inelastic neutron scattering, magnetic susceptibility, magnetization, and the magnetic field dependence of the specific heat for the heavy Fermion compounds Ce3In and Ce3Sn. The neutron scattering results show that the excited crystal field levels have energies E1 = 13.2 meV, E2 = 44.8 meV for Ce3In and E1 = 18.5 meV, E2 = 36.1 meV for Ce3Sn. The Kondo temperature deduced from the quasielastic linewidth is 17 K for Ce3In and 40 K for Ce3Sn. The low temperature behavior of the specific heat, magnetization, and susceptibility can not be welldescribed by J=1/2 Kondo physics alone, but require calculations that include contributions from the Kondo effect, broadened crystal fields, and ferromagnetic correlations, all of which are known to be important in these compounds. We find that in Ce3In the ferromagnetic fluctuation makes a 10-15 % contribution to the ground state doublet entropy and magnetization. The large specific heat coefficient γ in this heavy fermion system thus arises more from the ferromagnetic correlations than from the Kondo behavior.
On the ground state of the Kondo lattice system CeCu6
Solid State Communications, 1985
Magnetization measurements have been performed on a single crystal of CeCu6 along the three main crystallographic directions between 1.5 and 300 K. The results are interpreted in terms of a crystal field calculation slightly modified by a spin fluctuation contribution of Kondo origin. Anisotropic magnetic properties of the Kondo lattice are discussed.
CeNiAsO: an antiferromagnetic dense Kondo lattice
Journal of Physics: Condensed Matter, 2011
A cerium containing pnictide, CeNiAsO, crystallized in the ZrCuSiAs type structure, has been investigated by measuring transport and magnetic properties, as well as specific heat. We found that CeNiAsO is an antiferromagnetic dense Kondo lattice metallic compound with Kondo scale T K ∼ 15 K and shows an enhanced Sommerfeld coefficient of γ 0 ∼ 203 mJ/mol·K 2 . While no superconductivity can been observed down to 30 mK, Ce ions exhibit two successive antiferromagnetic (AFM) transitions. We propose that the magnetic moment of Ce ion could align in the G type AFM order below the first transition at T N 1 =9.3 K, and it might be modified into the C type AFM order below a lower transition at T N 2 =7.3 K. Our results indicate that the 3d-4f interlayer Kondo interactions play an important role in Ni-based Ce-containing pnictide.