Knight-shift anomalies in heavy-electron materials

Article

关键词: CONSISTENT PERTURBATION-THEORY;    DILUTE MAGNETIC-ALLOYS;    NON-FERMI-LIQUID;    KONDO SCREENING CLOUD;    RARE-EARTH-METALS;    LARGE-N EXPANSION;    ANDERSON MODEL;    SPIN-POLARIZATION;    VALENCE FLUCTUATIONS;    STATE PROPERTIES;   

DOI  :  10.1103/PhysRevB.58.3313

来源: SCIE

【 摘 要 】

We have studied the Knight shift K((r) over right arrow,T) and magnetic susceptibility chi(T) of heavy-electron materials, modeled by the infinite-U Anderson model with the noncrossing approximation method. A systematic study of K((r) over right arrow,T) and chi(T) for different Kondo temperatures T-0 (which depends on the hybridization width Gamma) shows a low-temperature anomaly (nonlinear relation between K and chi) which increases as the Kondo temperature T-0 and distance r increase. We carried out an incoherent lattice sum by adding the K((r) over right arrow) of a few hundred shells of rare-earth atoms around a nucleus and compare the numerically calculated results with the experimental results. For CeSn3, which is a concentrated heavy-electron material, both the Sn-119 NMR Knight shift and positive muon Knight shift are studied. Also, lattice coherence effects by conduction-electron scattering at every rare-earth site are included using the average-T-matrix approximation. The calculated magnetic susceptibility and Sn-119 NMR Knight shift show excellent agreement with experimental results for both incoherent and coherent calculations. The positive muon Knight shifts are calculated for both possible positions of muon (center of the cubic unit cell and middle of Ce-Ce bond axis). Our numerical results show a low-temperature anomaly for the muons of the correct magnitude but we can only find agreement with experiment if we take a weighted average of the two sites in a calculation with lattice coherence present. For YbCuAl, the measured Al-27 NMR Knight shift shows an anomaly with opposite sign to the CeSn3 compound. Our calculations agree very well with the experiments. For the proposed quadrupolar Kondo alloy Y0.8U0.2Pd3, our Y-89 NMR Knight-shift calculation do not show the observed Knight-shift anomaly.

【 授权许可】

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