Incommensurate Magnetic Order in Sm₃BWO₉ with Distorted Kagome Lattice

We investigate the magnetic ground state of Sm$_3$BWO$_9$ with distorted kagome lattice. A phase transition is identified at $T_N=0.75$ K from temperature dependence specific heat. From $^{11}$B nuclear resonance (NMR) measurements, an incommensurate order shown by double-horn type spectra under a $c$-axis field. While, absence line splitting observed for field oriented within $ab$-plane, indicating modulation internal strictly along $c$-axis. spin dynamics, critical slowing down behavior in $1/T_1$ $\mu_0H\perp c$-axis, which completely absent that $\mu_0H||c$-axis. Based on local symmetry sites, we analyze hyperfine coupling tensors and propose two constraints possible structure. The single ion anisotropy should play important role determination contrasting states Pr$_3$BWO$_9$.