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The relationship between charge density wave (CDW) orders and superconductivity in arsenide superconductor SrPt$_2$As$_2$ with $T_c$ = 5.2 K which crystallizes in the CaBe$_2$Ge$_2$-type structure was studied by $^{75}$As nuclear magnetic resonance (NMR) measurements up to 520 K, and $^{75}$As nuclear quadrupole resonance (NQR) and $^{195}$Pt-NMR measurements down to 1.5 K. At high temperature, $^{75}$As-NMR spectrum and nuclear spin relaxation rate ($1/T_1$) have revealed two distinct CDW orders, one realized in the As-Pt-As layer below $T_{rm CDW}^{rm As(1)}$ $=$ 410 K and the other in the Pt-As-Pt layer below $T_{rm CDW}^{rm As(2)}$ $=$ 255 K. The $1/T_1$ measured by $^{75}$As-NQR shows a clear Hebel-Slichter peak just below $T_c$ and decreases exponentially well below $T_c$. Concomitantly, $^{195}$Pt Knight shift decreases below $T_c$. Our results indicate that superconductivity in SrPt$_2$As$_2$ is in the spin-singlet state with an $s$-wave gap and is robust under the two distinct CDW orders in different layers.
Filled skutterudite compound EuFe$_4$As$_{12}$ shows the highest magnetic ordering temperature of $T_{rm C}$ = 154 K among Eu-based skutterudite compounds, but its magnetic ground state has not been determined yet. Here, we performed $^{153}$Eu nucle
We present the results of $^{75}$As nuclear magnetic resonance (NMR), nuclear quadrupole resonance (NQR), and resistivity measurements in KFe$_2$As$_2$ under pressure ($p$). The temperature dependence of the NMR shift, nuclear spin-lattice relaxation
We report systematic 57Fe-NMR and 75As-NMR/NQR studies on an underdoped sample (T_c=20 K), an optimally doped sample (T_c=28 K), and an overdoped sample (T_c=22 K) of oxygen-deficient iron (Fe)-based oxypnictide superconductor LaFeAsO_{1-y}$. A micro
$^{75}$As nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements have been carried out to investigate the magnetic and electronic properties of the filled skutterudite metallic compound SrFe$_4$As$_{12}$. The temperature
We report $^{125}$Te nuclear magnetic resonance and $^{181}$Ta nuclear quadrupole resonance studies on single-crystal Ta$_{4}$Pd$_{3}$Te$_{16}$, which has a quasi-one-dimensional structure and superconducts below $T_{rm c}=4.3$ K. $^{181}$Ta with spi