$^{11}$B Nuclear Magnetic Resonance Measurements of Antiferromagnetic DyB$_{4}$ Single Crystals

$^{11}$B pulsed nuclear magnetic resonance (NMR) measurements have been performed to investigate local electronic structures and $4f$ spin dynamics in antiferromagnetic DyB$_{4}$ single crystals. $^{11}$B NMR spectrum, Knight shift, spin-lattice and spin-spin relaxation rates, $1/T_{1}$ and $1/T_{2 }$, were measured down to 4.3 K under magnetic field of 8 T. The $^{11}$B NMR shift and linewidth are huge and strongly temperature-dependent due to $4f$ moments of Dy. In addition, both are proportional to magnetic susceptibility, indicating that the hyperfine field at the boron site originates from the $4f$ spins of Dy. Below$ T_{N}$ =20 K. the single broad resonance peak of $^{11}$B NMR splits into several peaks reflecting the local magnetic fields developed due to the antiferromagnetic spin arrangement. The relaxation rates $1/T_{1}$ and $1/T_{2}$ are very large and independent of temperature much above $T_{N}$ and then decrease significantly below $T_{N }$ confirming the suppression of spin fluctuation and the huge change in $4f$ spin dynamics associated with the antiferromagnetic ordering.