Giant Nuclear-Electronic Spin Pumping in the Heisenberg Antiferromagnet RbMnF 3 J. D. M. de Lima , 1,* D. S. Maior , 1 E. C. Souza , 1 D. R. Ratkovski , 1 F. L. A. Machado , 1 R. L. Rodríguez-Suárez , 2 and S. M. Rezende 1 1 Departamento de Física, Universidade Federal de Pernambuco, 50670-901 Recife, Pernambuco, Brazil 2 Facultad de Física, Pontificia Universidad Católica de Chile, Casilla 306, Correo 22, Santiago, Chile (Received 25 August 2024; accepted 20 March 2025; published 9 April 2025) 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. DOI: 10.1103/PhysRevLett.134.146702 The spin pumping process in a magnetic material consists of the emission of an electronic spin-angular momentum current, or spin current, by a time-varying magnetization, such as in the precession produced by ferro- magnetic resonance. The electronic spin pumping was conceived two decades ago as a mechanism for the mag- netization damping in ferromagnetic (FM) and non- magnetic metal (NM) bilayers [1–3]. However, a more interesting effect of the spin pumping was soon discovered experimentally, namely, the generation of an electric voltage in the NM layer resulting from the conversion of the injected spin current into a charge current by means of the inverse spin Hall effect (ISHE) [4–10]. Later, this phenomenon was predicted [11,12] and demonstrated experimentally in bilayers made of an antiferromagnetic insulator (AFI) and a NM layer [13,14], contributing to boost the emerging field of antiferromagnetic spintronics [15–24]. These effects have become some of the most important ones in the active field of spintronics, which has applications in magnetic memory devices and has the possibility to become a robust and energy-efficient way to deal with classical and quantum information. Recently, it has been reported by Shiomi et al. [25] that the nuclear magnetic resonance (NMR) in the insulating antiferromagnet MnCO 3 can also produce spin pumping, which by means of the hyperfine interaction is converted into an electronic spin current that is injected into an adjacent metallic layer and detected electrically by the ISHE. The material used in the experiments is an aniso- tropic antiferromagnet that has the two sublattice spins in a canted configuration due to the presence of a bulk Dzyaloshinskii-Moriya interaction [26–29], regardless of the value of the applied magnetic field. As in other mag- netic materials, in MnCO 3 the Suhl-Nakamura interaction [30–32] leads to an indirect coupling between the nuclear spins that give rise to nuclear spin waves that have attracted considerable attention for several years [33–49]. The observations of spintronic phenomena produced by nuclear spin waves in antiferromagnets open new possibilities in spintronics by combining the advantages of the long-lived nuclear spin states with the information technology readily available through spintronic devices [50]. In this Letter, we report the observation of strong nuclear-electronic spin pumping effects in the insulating antiferromagnet RbMnF 3 , a two-sublattice antiferromagnet with the Mn 2þ magnetic ions having 100% abundance of the 55 Mn magnetic isotope, which has been widely studied with nuclear magnetic resonance techniques [51–57]. Because of the cubic crystal structure [Fig. 1(a)], where the dipolar field in the center of the unit cell vanishes, and the fact that the Mn 2þ magnetic ions have electronic ground * Contact author: marques.lima@ufpe.br PHYSICAL REVIEW LETTERS 134, 146702 (2025) 0031-9007=25=134(14)=146702(6) 146702-1 © 2025 American Physical Society