High-Frequency Spin Pumping from Insulating Antiferromagnet MnF₂

Antiferromagnetic materials, particularly antiferromagnetic insulators provide an alternative to present ferromagnetic spin-transfer torque based devices which suffer from limitations in terms of density (e.g., because neighboring units can couple through stray fields) and speed (frequencies are limited to the GHz range). In contrast to ferromagnets, where magnetic anisotropy dominates spin dynamics, in antiferromagnets spin dynamics are governed by the interatomic exchange interaction energies which are orders of magnitude larger than the magnetic anisotropy energy, leading to the potential for ultrafast information processing and communication in the THz frequency range. We will present studies of spin pumping at Manganese Difluoride(MnF₂) / Platinum (Pt) interfaces at temperatures below the MnF₂ Néel temperature (T_N = 67.34K). In particular, measurements of the inverse spin Hall effect (ISHE) voltage arising from the interconversion of the dynamically injected spin currents into Pt will be reported. We observe a clear electrostatic potential signal coinciding with the MnF₂ spin-flop transition (H_SF = 9T). The signal reverses by switching the polarity of the magnetic field, and displays a marked dependence on the power of the microwave stimuli, as expected from the ISHE.