μSR and NMR in f-electron non-Fermi liquid materials

• Published in: Physica. B, Condensed matter Condensed matter, 2003-02, Vol.326 (1), p.381-386
• Main Authors: MacLaughlin, D.E., Rose, M.S., Young, Ben-Li, Bernal, O.O., Heffner, R.H., Morris, G.D., Ishida, K., Nieuwenhuys, G.J., Sonier, J.E.
• Format: Article
• Language: English
• Subjects: CePtSi 1− xGe x; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Disorder-driven mechanisms; Exact sciences and technology; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Muon spin rotation and relaxation; Non-Fermi liquids; Nuclear magnetic resonance and relaxation; Physics; Quantum critical points
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/S0921-4526(02)01637-X

Magnetic resonance (μSR and NMR) studies of f-electron non-Fermi-liquid (NFL) materials give clear evidence that structural disorder is a major factor in NFL behavior. Longitudinal-field μSR relaxation measurements at low fields reveal a wide distribution of muon relaxation rates and divergences in the frequency dependence of spin correlation functions in the NFL systems UCu 5− x Pd x and CePtSi 1− x Ge x . These divergences seem to be due to slow dynamics associated with quantum spin-glass behavior, rather than quantum criticality as in a uniform system, for two reasons: the observed strong inhomogeneity in the muon relaxation rate, and the strong and frequency-dependent low-frequency fluctuation observed in U(Cu,Pd) 5 and CePt(Si,Ge). In the NFL materials CeCu 5.9Au 0.1, Ce(Ru 0.5Rh 0.5) 2Si 2, CeNi 2Ge 2, and YbRh 2Si 2 the low-frequency weight of the spin fluctuation spectrum is much weaker than in the disordered NFL systems.