Magnetic Hyperfine Fields at Se Adatoms on Ni Surfaces

Magnetic hyperfine fields for Se on Ni(111) and Ni(001) surfaces were measured with the perturbed angular correlation technique. The results are $|{B}_{\mathrm{hf}}|\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.7(3)$ T for Se on Ni(111) and $|{B}_{\mathrm{hf}}|\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0.8(3)$ T for Se on Ni(001) at 90 K. These values of magnetic hyperfine fields of an adatom deviate drastically from the known bulk value of ${B}_{\mathrm{hf}}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}15\mathrm{T}$. The surface site positions of the probe atoms are discussed with the aid of the results for the electric hyperfine interactions measured simultaneously.