Quadrupolar Ordering in YbSb Studied by ^<121>Sb and ^<123>Sb NMR(Condensed Matter : Electronic Structure, Electrical, Magnetic and Optical Properties)

概要

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NMR measurements of ^<121>Sb and ^<123>Sb nuclei have been performed in a heavy-fermion compound YbSb to investigate a phase transition around 5 K from the microscopic point of view. The nuclear magnetic relaxation rate (T^<-1>_1) shows a distinct increase around the transition temperature. The isotope ratio ^<123>(T^<-1>_1)/^<121>(T^<-1>_1) shows that the increase of the relaxation rate is mainly ascribed to fluctuations of the electric field gradient at Sb sites. This supports the proposal that the phase transition around 5 K is due to quadrupolar ordering. A large broadening of the NMR spectra is observed below the transition temperature, furthermore, the width continues to increase anomalously when the temperature is decreased, in contrast with usual magnetic orderings. This anomalous temperature dependence of the width is well explained by calculations using the molecular field approximation including the crystal field potential and intersite quadrupolar interactions.
社団法人日本物理学会の論文
2004-07-15