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#### Dynamical susceptibility and magnetic-field effect at the quantum critical point in CeCu_{6-x}Au_{x} from Cu NQR-NMR relaxation

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##### Citation

Carretta, P., Giovannini, M., Horvatić, M., Papinutto, N., & Rigamonti, A. (2003).
Dynamical susceptibility and magnetic-field effect at the quantum critical point in CeCu_{6-x}Au_{x} from
Cu NQR-NMR relaxation.* Physical Review B,* *68*: 220404.

Cite as: https://hdl.handle.net/21.11116/0000-000E-E887-4

##### Abstract

Cu-63,Cu-65 NQR-NMR relaxation measurements in CeCu6-xAux for x=0,

x=0.1, and x=0.8 are used to derive insights on temperature (T) and

magnetic-field (H) dependences of the spin dynamics around the quantum

critical point (QCP). The relaxation rate 2W is related to the k

integrated, low energy, generalized susceptibility

chi(k,omega,H,T-->0). For x=0 a Fermi-liquid behavior is detected,

while for x=0.8 the temperature dependence of 2W is the one expected

for a nearly antiferromagnetic metal ordering at T-N=2.2 K. Instead,

for x=0.1, around the QCP, a response function of the form suggested by

neutron scattering, namely of two-dimensional character with anomalous

exponent and (omega/T) scaling, is found to explain the main

experimental findings. An effect is observed in the low-temperature

range for Hgreater than or similar to1 T, with a crossover to a gapped

phase for the spin excitations at a field-dependent temperature.

x=0.1, and x=0.8 are used to derive insights on temperature (T) and

magnetic-field (H) dependences of the spin dynamics around the quantum

critical point (QCP). The relaxation rate 2W is related to the k

integrated, low energy, generalized susceptibility

chi(k,omega,H,T-->0). For x=0 a Fermi-liquid behavior is detected,

while for x=0.8 the temperature dependence of 2W is the one expected

for a nearly antiferromagnetic metal ordering at T-N=2.2 K. Instead,

for x=0.1, around the QCP, a response function of the form suggested by

neutron scattering, namely of two-dimensional character with anomalous

exponent and (omega/T) scaling, is found to explain the main

experimental findings. An effect is observed in the low-temperature

range for Hgreater than or similar to1 T, with a crossover to a gapped

phase for the spin excitations at a field-dependent temperature.