11B and 195Pt NMR study of heavy-fermion compound CePt2B2C
TL;DR: In this article, the authors reported 11B and 195Pt NMR Knight shift K and spin?lattice relaxation rate 1/T1 in CePt2B2C in the range 4?315?K.
Abstract: We report 11B and 195Pt NMR Knight shift K and spin?lattice relaxation rate 1/T1 in CePt2B2C in the range 4?315?K. The quadrupolar coupling constant, ?Q for boron nuclei is 790 ? 10?kHz. The change of hyperfine field, Hhf, is observed below 30?K in the K versus susceptibility, ?, plot. The calculated value of Hhf at the 11B (195Pt) is 0.156 (6.86) kOe/?B in the range 30?300?K and ~0 (0.22) kOe/?B below 30?K. The 1/T1 versus T curve shows some exotic behavior. The Ce?4f spin contribution to the nuclear relaxation rate (1/T1f) in each case is obtained by subtracting the T1K?1 estimated from its La analog, i.e.?LaPt2B2C. In the case of 11B resonance, in the temperature range of 300?100?K, (1/T1f) is independent of T, suggesting a Curie?Weiss behavior of the imaginary part of the dynamic susceptibility. It then shows a slow but continuous increment in the range 100?70?K, indicating a signature of the development of short-range magnetic correlation among the Ce?4f spins. Below 70?K, this enhancement of 1/T1f is completely suppressed and it decreases sharply, indicating a suppression of the effect of magnetic correlation, due to the dominance of the Kondo effect over the RKKY interaction. 1/T1f, follows ~T?, with an exponent ?~0.7 in the range 4?30?K for 195Pt and in the range 8?30?K for 11B resonance. This is a characteristics of a non-Fermi-liquid like behavior. However, in the case of 11B, there is again a clear change in the slope of the 1/T1f versus T curve below 8?K, with the value of ? = 1.0, as if the behavior of the conduction electrons approaches towards a Fermi liquid, when probed near the 11B site.
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TL;DR: In this article , the effect of Ir substitution by Ni on the boron arrangement of these borides, primarily due to its weak scattering factor, was investigated using 11B-NMR.
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TL;DR: In this article, the Anderson hamiltonian was used to describe the behavior of magnetic impurities in real metals, taking into account the orbital structure of the local impurity electrons, crystal field and spin orbit splittings.
Abstract: Starting from the most general form of the Anderson hamiltonian, the behaviour of magnetic impurities in real metals is considered, taking into account the orbital structure of the local impurity electrons, crystal field and spin orbit splittings. The analysis is carried out in an atomic limit, in which the impurity has a well defined integer valency (a Schrieffer Wolff transformation is then valid). The main steps of a scaling procedure are described in detail. As the temperature goes down, the excited states of the ground state configuration decouple one after the other. The hierarchy of these decouplings, and their interplay with Kondo singularities are analyzed. When a Fermi liquid picture applies as T → 0, the number of independent parameters may be reduced considerably using symmetry and universality arguments which bypass the numerical description of the crossover region. That first part sets a language in which to describe specific problems. We apply that language to the case where the atomic ground state is an orbital singlet. In the absence of anisotropies, the only parameters are the impurity spin S and the number of orbital channels n. We show that an anomalous fixed point occurs at finite coupling when n > 2 S. That fixed point is unstable with respect to anisotropies. The scaling trajectories are discussed for a cubic crystal field for several choices of valencies. The universality of the low temperature behaviour is clarified. A similar analysis is carried out when the atomic ground state only has one electron (or hole). The influence of crystal field and spin orbit interactions is analyzed — and their relevance to the Kondo crossover and to universality is ascertained.
659 citations
TL;DR: In this article, the first observation of non-Fermi-liquid effects in a clean Yb compound at ambient pressure and zero magnetic field was reported, and the authors ascribe this NFL behavior to the presence of quasi-2D antiferromagnetic spin fluctuations related to a very weak magnetic phase transition at T(N) approximately 65 mK.
Abstract: We report the first observation of non-Fermi-liquid (NFL) effects in a clean Yb compound at ambient pressure and zero magnetic field. The electrical resistivity and the specific-heat coefficient of high-quality single crystals of YbRh(2)Si(2) present a linear and a logarithmic temperature dependence, respectively, in more than a decade in temperature. We ascribe this NFL behavior to the presence of (presumably) quasi-2D antiferromagnetic spin fluctuations related to a very weak magnetic phase transition at T(N) approximately 65 mK. Application of hydrostatic pressure induces anomalies in the electrical resistivity, indicating the stabilization of magnetic order.
467 citations
TL;DR: The possibility of an electric quadrupole Kondo effect for a non-Kramers doublet on a uranium (U) ion in a cubic metallic host is demonstrated by model calculations showing a Kondo upturn in the resistivity, universal quenching of the quadrupolar moment, and a heavy electron anomaly in the electronic specific heat.
Abstract: The possibility of an electric quadrupole Kondo effect for a non-Kramers doublet on a uranium (U) ion is a cubic metallic host is demonstrated by model calculations showing a Kondo upturn in the resistivity, universal quenching of the quadrupolar moment, and a heavy-electron anomaly in the electronic specific heat. With inclusion of excited crystal-field levels, some of the unusual magnetic-response data in the heavy-electron superconductor UBe13 may be understood. Structural phase transitions at unprecedented low temperatures may occur in U-based heavy-electron materials.
453 citations
TL;DR: In this article, a simple phenomenological model with a distribution of Kondo temperatures fits the field and the temperature dependence of the susceptibility, and then describes the copper NMR linewidth semiquantitatively with no further adjustable parameters.
Abstract: Strong inhomogeneous broadening of the copper NMR line in ${\mathrm{UCu}}_{5\ensuremath{-}x}{\mathrm{Pd}}_{x}$, $x\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1.0$ and 1.5, indicates that spin susceptibility disorder contributes to the non-Fermi-liquid behavior of these alloys. A simple phenomenological model with a distribution of Kondo temperatures fits the field and the temperature dependence of the susceptibility, and then describes the copper NMR linewidth semiquantitatively with no further adjustable parameters. The temperature and the field dependence of the specific heat also agree well with the model.
186 citations
TL;DR: In this paper, a model of disordered Anderson lattices can account for many non-Fermi-liquid features observed in some Kondo alloys because of the exponential nature of the Kondo temperature scale T{sub K], even moderate disorder leads to a rather broad distribution of Kondo temperatures, inducing strong conduction electrons.
Abstract: We show how a model of disordered Anderson lattices can account for many non-Fermi-liquid features observed in some Kondo alloys Because of the exponential nature of the Kondo temperature scale T{sub K}, even moderate disorder leads to a rather broad distribution of Kondo temperatures, inducing strong {ital effective} disorder seen by the conduction electrons Spins with very low T{sub K}`s remain unquenched and dominate the low-temperature propertiesThis single underlying mechanism leads to logarithmic divergences in thermodynamic quantities and a linear temperature dependence of the resistivity {copyright} {ital 1997} {ital The American Physical Society}
160 citations