Physical Review Letters
Mössbauer-effect and microwave absorption experimental evidence unambiguously demonstrates the presence of slow, ∼450 MHz, tunneling of magnetic europium between four equivalent sites in Eu8Ga16Ge30, a stoichiometric clathrate. Remarkably, six of the eight europium atoms, or 11% of the constituents in this solid, tunnel between these four sites separated by 0.55 Å. The off centering of the atoms or ions in crystalline clathrates appears to be a promising route for producing Rabi oscillators in solid-state materials.
Hermann, Raphaël P.; Keppens, Veerle; Bonville, Pierre; Nolas, George S.; Grandjean, Fernande; Long, Gary J.; Christen, Hans M.; Chakoumakos, Bryan C.; Sales, Brian C.; and Mandrus, David, "Direct Experimental Evidence for Atomic Tunneling of Europium in Crystalline Eu8Ga16Ge30" (2006). Faculty Publications and Other Works -- Materials Science & Engineering.