$^{11}$B NMR Measurements of TbB$_4$

$^{11}$B pulsed NMR measurements have been performed to investigate local electronic structure and 4f spin dynamics for TbB$_4$ single crystals. $^{11}$B NMR spectrum shows a broad peak due to the 4f local moment. $^{11}$B NMR shift and linewidth are huge and strongly temperature-dependent. In addition, both are proportional to magnetic susceptibility, indicating that the hyperfine field at the boron site originates from the 4f spins of Tb. The shift and the spin- lattice relaxation rate show high anisotropy for field parallel and perpendicular to the c-axis. Anisotropy of the shift and the relaxation rates are analyzed with the results of magnetization to understand the microscopic details of anisotropic spin dynamics.