Giant Nuclear-Electronic Spin Pumping in the Heisenberg Antiferromagnet RbMnF_{3}

Collective nuclear spin excitations, called nuclear spin waves, or nuclear magnons, are enabled in strongly magnetic materials by the hyperfine coupling between the nuclear and electronic spins in an atom, and the exchange interaction between electronic spins. The investigation of nuclear spin waves garnered significant interest from theoretical and experimental researchers worldwide during the 1970s and 1980s, but gradually waned in prominence. Recently, it has been reported that the nuclear magnetic resonance in the canted antiferromagnet MnCO_{3} produces spin pumping effects similar to the ones studied in ferro- and antiferromagnetic materials, bridging two quite separate worlds, the one of nuclear spin excitations and the other of spintronics. In this Letter, we report the observation of giant nuclear-electronic spin pumping effects driven by radio frequencies in the Heisenberg antiferromagnet RbMnF_{3}. In this material, the small values of the electronic magnon frequencies in the vicinity of the antiferromagnetic or spin-flop transition result in an enhanced frequency pulling of the nuclear magnetic resonance frequencies that produces a strong coupling between the nuclear and electronic spin degrees of freedom. This results in nuclear-electronic spin pumping signals in the Heisenberg antiferromagnet RbMnF_{3} that are almost 2 orders of magnitude larger than in MnCO_{3} and remain visible at temperatures nearly 10 times higher. A theory for the nuclear-electronic spin pumping process accounts well for the experimental results.