Magnetic Field Evolution of a Novel Phase Transition in CeOs4Sb12: Sb-121 NMR Study

概要

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We report on the evolution of a novel phase transition under magnetic field ($H$) in the filled skutterudite compound CeOs4Sb12 probed by 121Sb NMR. Measurements of nuclear spin–lattice relaxation rate $^{121}(1/T_{1})$ for the oriented powder with $H\parallel[100]$ have revealed that antiferromagnetic (AFM) spin fluctuations due to the proximity of a quantum critical point at $H=0$ are markedly suppressed by the application of $H$, which is consistent with the result indicating that the AFM order at $T_{\text{N}}=0.9$ K with a very small moment of $0.07\mu_{B}$ collapses, exceeding $H=1$ T. As $H$ increases further, a large reduction in $1/T_{1}T$ was observed below the temperature $T_{0}$, which varies as a dome against $H$ with a maximum of 1.8 K at $H\sim 6$ T. The values of $T_{1}T=\text{const.}$ well below $T_{0}$ decrease with increasing $H$, indicating that the residual density of states depends on $H$. It is suggested that the field-induced novel transition is associated with the freezing of multipole degree of freedom.
Physical Society of Japanの論文
2009-05-15