Effective control and probe of Néel order in polycrystalline NiO films: a combined approach to study antiferromagnets.

Antiferromagnetic (AFM) materials are promising for next-generation spintronic applications, however, practical implementation remains challenging due to difficulties in controlling the Néel order and the lack of sensitive, device-compatible readout techniques. In this work, we demonstrate spin Hall magnetoresistance (SHMR) as an effective and versatile approach for probing Néel order, even in polycrystalline AFM films. Using NiO/Pt and LaNiO3/Pt bilayers as model systems, we show that SHMR measurements can detect the Néel temperature (TN), monitor spin-flop transition, and reveal field-induced orientation of the Néel order. Crucially, we establish that the control of Néel order with non-volatility is effective when initiated from the “soft” AFM phase at elevated temperature (380 K) via field-cooling (FC), enabling robust alignment of Néel order without the need for adjacent heavy metals as spin current sources. This spin-current-free control greatly expands the flexibility and scalability of AFM device design, especially in the form of polycrystalline microstructure. The results highlight the combined FC and SHMR technique as a powerful and flexible platform for both manipulation and sensitive readout of AFM states, providing a reliable basis for the design and characterization of a broad class of AFM materials and devices.