Novel Phase Transition Near the Quantum Critical Point in the Filled-Skutterudite Compound CeOs4Sb12: an Sb-NQR Study

TL;DR

This study uncovers a first-order phase transition at 0.9 K in CeOs4Sb12, linked to antiferromagnetic quantum criticality, revealed through Sb-NQR measurements showing spectral broadening and relaxation rate changes.

Contribution

It demonstrates a novel phase transition near the AFM quantum critical point in CeOs4Sb12 using Sb-NQR, highlighting the role of correlated f-electron bands.

Findings

First-order phase transition at 0.9 K evidenced by NQR spectrum broadening.

Relaxation rate 1/T1 approaches behavior near AFM QCP.

Transition linked to SDW or CDW order in CeOs4Sb12.

Abstract

We report on a novel phase transition at $T$ = 0.9 K in the Ce-based filled-skutterudite compound CeOs$_{4}$Sb$_{12}$ via measurements of the nuclear-spin lattice relaxation rate $1/T_{1}$ and nuclear quadrupole resonance (NQR) spectrum of Sb nuclei. The temperature ($T$) dependence of $1/T_1$ behaves as if approaching closely an antiferromagnetic (AFM) quantum critical point (QCP), following the relation $1/T_{1}\propto T/(T-T_{\rm N})^{1/2}$ with $T_{\rm N} = 0.06$ K in the range of $T=1.3-25$ K. The onset of either the spin-density-wave (SDW) or charge-density-wave (CDW) order at $T_{\rm 0} = 0.9$ K, that is, of the first order, is evidenced by a broadening of the NQR spectrum and a marked reduction in $1/T_1$ just below $T_{\rm 0}$. The $f$-electron-derived correlated band realized in CeOs$_{4}$Sb$_{12}$ is demonstrated to give rise to the novel phase transition on the verge of AFM QCP.