Nuclear Zeeman Effect in Gold Atoms Dissolved in Iron, Cobalt, and Nickel

The nuclear Zeeman effect has been observed in Au¹⁹⁷ nuclei dissolved in ferromagnetic hosts, using the M\"ossbauer effect. The magnetic moment of the 77-keV isomeric state of Au¹⁹⁷ was measured as μ=+0.37 (4) nm. The hyperfine magnetic fields at Au nuclei dissolved in iron, hexagonal cobalt, cubic cobalt, and nickel were found to be -1420 (180), -980 (120), -990 (120), and -340 (60) kG, respectively, by comparison with external magnetic fields up to 86 kG. Experiments in low external fields gave an unexpected result which is interpreted in terms of magnetostriction in the ferromagnetic sources.