CeCoIn $_5$的超低温NMR
Ultralow temperature NMR of CeCoIn$_5$
摘要：
我们已经进行了$^{59}$钴核磁共振测量CeCoIn $_5$下降到超低温。我们发现，自旋回波强度的温度依赖性提供了一个很好的测量样品的温度，使我们能够确定一个脉冲条件不加热的样品的NMR脉冲下降到超低温。从沿$c$轴施加的5 T下的纵向弛豫时间（$T_1$）测量，在20 mK下观察到$1/T_1T$的明显峰，这意味着磁有序的出现，如最近的量子振荡测量所建议的[H. Shishido { \it等}，物理修订版信函{ \bf 120}，177201（2018）]。另一方面，NMR谱在20 mK以下没有显示变化。此外，与量子振荡的结果相反，$1/T_1 T$中的峰在6和8 T处消失。我们讨论了一个磁矩位于$a$-$b$平面的反铁磁态可能是$1/T_1 T$在5 T下的峰的起源。
英文摘要：
We have performed $^{59}$Co NMR measurements of CeCoIn$_5$ down to ultralow temperatures. We find that the temperature dependence of the spin-echo intensity provides a good measure of the sample temperature, enabling us to determine a pulse condition not heating up the sample by the NMR pulses down to ultralow temperatures. From the longitudinal relaxation time ($T_1$) measurements at 5 T applied along the $c$ axis, a pronounced peak in $1/T_1T$ is observed at 20 mK, implying an appearance of magnetic order as suggested by the recent quantum oscillation measurements [H. Shishido {\it et al.}, Phys. Rev. Lett. {\bf 120}, 177201 (2018)]. On the other hand, the NMR spectrum shows no change below 20 mK. Moreover, the peak in $1/T_1 T$ disappears at 6 and 8 T in contrast to the results of the quantum oscillation. We discuss that an antiferromagnetic state with a moment lying in the $a$--$b$ plane can be a possible origin for the peak in $1/T_1 T$ at 5 T.
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