Synthetic staggered fields switch Neel vectors probed by magnetic resonance
Electrical detection of antiferromagnetic order is a critical challenge for antiferromagnetic spintronics owing to their vanishing macroscopic magnetisation. While magnetic resonance has demonstrated sub-terahertz antiferromagnetic spin pumping and nonlinear magnon dynamics, its application to electrically contacted on-chip devices has room for further exploration. Here we show that magnetic resonance enables direct electrical detection of Néel vector states. A $180^\circ$ reversal in synthetic antiferromagnets is realised by current-driven effective fields with opposite polarisation acting on each magnetic sublayer, which we term synthetic staggered fields. The switching induces a $π$ phase shift of precessional motion in time, producing hysteretic rectified voltages in our phase-sensitive detection scheme. Angular-dependent resonance analysis offers further insight into the Néel vector directions, pointing to a model beyond the macrospin formalism. We address this by defect-incorporated micromagnetic simulations that reveal fragmented domain states after current excitation. An extracted current density of $7.4\times10^{9}$ A/m$^2$ is, to our knowledge, the lowest reported value for the room-temperature Néel vector switching and we show that it scales with the in-plane uniaxial anisotropy both experimentally and numerically. Synthetic staggered fields and the resonance-based methodology provide a research platform for nanoscale characterisation of electrically driven antiferromagnetic textures, guiding the development of high-frequency on-chip spintronic architectures.