Electrical readout of coherent spin dynamics in an antiferromagnet*

Demonstration of spin pumping [1] in antiferromagnets (AFMs) was an important milestone in AFM spintronics. As the next step, it is imperative to achieve electrical readout of ultrafast spin dynamics that would be scalable to nano-size devices, thus paving the road to AFM-based spin-torque applications [2,3]. Here we systematically study the magnetoresistive spin-to-charge conversion of coherent spin dynamics at the interface of AFM and heavy-metal (HM). Using e-beam lithography and ion-milling, we prepare Hall-bars from 5 nm Pt films on the surface of Cr2O3 bulk crystals with magnetic easy-axis, [0001], parallel and perpendicular to the AFM/HM interface. By applying magnetic field along the easy-axis, we strongly lower the AFM magnon frequencies. Using monochromatic excitation in the range of 0-40 GHz, we coherently excite the left-hand magnon mode below the spin-flop (SF) field which transitions into the Goldstone-like mode above the SF. Both modes are detected simultaneously by magnetoresistance of Pt and by induction. We demonstrate detection by longitudinal and transverse magnetoresistance and evaluate it as a function of microwave power, DC current, temperature, and crystallographic orientation of the AFM/HM interface. Our results show how electrical readout of AFM spin dynamics paves the road toward AFM spin-torque devices.

[1] Junxue Li et al., Nature 578, 70 (2020) and P. Vaidya et al., Science 368, 160 (2020)

[2] R. Rodriguez et al., Phys. Rev. Research 4, 033139 (2022)

[3] A. Etesamirad et al., ACS Appl. Mater. Interfaces 13, 20288 (2021)