Localized $5f$ antiferromagnetism in cubic UIn$_{3}$: $^{115}$In-NMR/NQR Study

$^{115}$In nuclear magnetic resonance (NMR) and nuclear quadrupole resonance (NQR) measurements have been performed on an antiferromagnet UIn$_3$ with the cubic AuCu$_3$-type structure. The NQR frequency ($\nu_{\rm Q}$) and Knight shift ($K$) of $^ {115}$In in UIn$_3$ have been estimated in the paramagnetic state from NMR experiments under applied field. The perpendicular component of transferred hyperfine coupling constant ($A_\perp$) has been deduced from scaled behavior of $K$ to the static susceptibility ($\chi$). Under zero field, the observation of the NQR spectrum has led to an estimated $\nu_ {\rm Q}$ of 11.8 MHz at 90 K. The temperature variation of the NQR relaxation rates ($1/T_1$) far above the N{\'e}el temperature $T_{\rm N}$=88 K approaches a constant value, which indicates a localized nature for the $5f$- electrons in this system. On the other hand, in the antiferromagnetically ordered state at 4 K (well below $T_ {\rm N}$), the $^{115}$In-NMR spectrum has been scanned over frequencies ranging from $\sim$20 to $\sim$70 MHz under zero applied field. From the analysis of the NMR spectrum, we propose that the direction of U moments in the AF state is neither $\langle 100 \rangle$ nor $\langle 111 \rangle$, but may be $\langle 110 \rangle$.