Research Article

Subterahertz spin pumping from an insulating antiferromagnet

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Science  10 Apr 2020:
Vol. 368, Issue 6487, pp. 160-165
DOI: 10.1126/science.aaz4247

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A spin-pumping antiferromagnet

Antiferromagnets have been used in spintronics mainly as a source of the so-called exchange bias. However, they hold promise for a much more active role given that their magnetization dynamics can in principle be much faster than those in ferromagnets. For this promise to materialize, antiferromagnets must learn the tricks that come naturally to ferromagnets. Vaidya et al. observed one such phenomenon called spin pumping (see the Perspective by Hoffmann). The researchers irradiated the antiferromagnet MnF2 with circularly polarized subterahertz light, causing the spins in this material to spring into action. These dynamics, in turn, caused the injection of spin current into a layer of platinum adjacent to MnF2.

Science, this issue p. 160; see also p. 135

Abstract

Spin-transfer torque and spin Hall effects combined with their reciprocal phenomena, spin pumping and inverse spin Hall effects (ISHEs), enable the reading and control of magnetic moments in spintronics. The direct observation of these effects remains elusive in antiferromagnetic-based devices. We report subterahertz spin pumping at the interface of the uniaxial insulating antiferromagnet manganese difluoride and platinum. The measured ISHE voltage arising from spin-charge conversion in the platinum layer depends on the chirality of the dynamical modes of the antiferromagnet, which is selectively excited and modulated by the handedness of the circularly polarized subterahertz irradiation. Our results open the door to the controlled generation of coherent, pure spin currents at terahertz frequencies.

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