Evidence of non-degenerated, non-reciprocal and ultra-fast spin-waves in the canted antiferromagnet {\alpha}-Fe2O3

Spin-waves in antiferromagnets hold the prospects for the development of faster, less power-hungry electronics, as well as new physics based on spin-superfluids and coherent magnon-condensates. For both these perspectives, addressing electrically coherent antiferromagnetic spin-waves is of importance, a prerequisite that has so far been elusive, because unlike ferromagnets, antiferromagnets couple weakly to radiofrequency fields. Here, we demonstrate the electrical detection of ultra-fast non-reciprocal spin-waves in the dipolar-exchange regime of a canted antiferromagnet. Using time-of-flight spin-wave spectroscopy on hematite (alpha-Fe2O3), we find that the magnon wave packets can propagate as fast as 30 km/s for reciprocal bulk spin-wave modes and up to 10 km/s for surface-spin waves propagating parallel to the antiferromagnetic N\'eel vector. The electrical detection of coherent non-reciprocal antiferromagnetic spin waves holds makes hematite a versatile platform where most of the magnonic concepts developed for ferromagnet can be adapted paving the way for the development antiferromagnetic and altermagnet-based magnonic devices.