Revealing the Hidden Hyperfine Interactions in ϵ-Iron

Herein, evidence for the long-sought finite hyperfine interaction in the high-pressure hexagonal close-packed ε-iron is gained through synchrotron radiation perturbed angular correlation spectroscopy. This method yields an energy splitting of 3.5(5)neV between the m _{I e} = ± 1/2 and m _{I e} = ± 3/2 nuclear sublevels of the iron-57 14.412-keV nuclear excited state at 30(1)GPa and room temperature. This energy splitting is related to a nuclear quadrupole hyperfine interaction with an electric field gradient of eq=1.2(2) x 10 ¹⁶ V/cm ² . However, there is still a possibility that the splitting of the iron-57 nuclear levels is related to a modest magnetic hyperfine interaction of ca. 0.40(5) T.