SrFeO x (SFO x ) compounds exhibit ionic conduction and oxygen-related phase transformation, having potential applications in solid oxide fuel cells, smart windows, and memristive devices. The phase transformation in SFO x typically requires a thermal annealing process under various pressure conditions, hindering their practical applications. Here, we have achieved a reversible phase transition from brownmillerite (BM) to perovskite (PV) in SrFeO2.5 (SFO2.5) films through ionic liquid (IL) gating. The real-time phase transformation is imaged using in situ high-resolution transmission electron microscopy. The magnetic transition in SFO2.5 is identified by fabricating an assisted La0.7Sr0.3MnO3 (LSMO) bottom layer. The IL-gating-converted PV phase of a SrFeO3−δ (SFO3−δ) layer shows a ferromagnetic-like behavior but applies a huge pinning effect on LSMO magnetic moments, which consequently leads to a prominent exchange bias phenomenon, suggesting an uncompensated helical magnetic structure of SFO3−δ. On the other hand, the suppression of both magnetic and exchange coupling signals for a BM-phased SFO2.5 layer elucidates its fully compensated G-type antiferromagnetic nature. We also demonstrated that the phase transition by IL gating is an effective pathway to tune the resistive switching parameters, such as set, reset, and high/low-resistance ratio in SFO2.5-based resistive random-access memory devices.

Synthetic antiferromagnets (SAF) have been proposed to replace ferromagnets in magnetic memory devices to reduce the stray field, increase the storage density and improve the thermal stability. Here we investigate the spin-orbit torque in a perpendicularly magnetized Pt/[Co/Pd]/Ru/[Co/Pd] SAF structure, which exhibits completely compensated magnetization and an exchange coupling field up to 2100 Oe. The magnetizations of two Co/Pd layers can be switched between two antiparallel states simultaneously by spin-orbit torque. The magnetization switching can be read out due to much stronger spin-orbit coupling at bottom Pt/[Co/Pd] interface compared to its upper counterpart without Pt. Both experimental and theoretical analyses unravel that the torque efficiency of antiferromagnetic coupled stacks is significantly higher than the ferromagnetic counterpart, making the critical switching current of SAF comparable to the conventional single ferromagnet. Besides adding an important dimension to spin-orbit torque, the efficient switching of completely * Present address:

We demonstrate spin-orbit torque (SOT) switching of amorphous CoTb single layer films with perpendicular magnetic anisotropy (PMA). The switching sustains even the film thickness is above 10 nm, where the critical switching current density keeps almost constant. Without the need of overcoming the strong interfacial Dzyaloshinskii-Moriya interaction caused by the heavy metal, a quite low assistant field of ~20 Oe is sufficient to realize the fully switching. The SOT effective field decreases and undergoes a sign change with the decrease of the Tb-concentration, implying that a combination of the spin Hall effect from both Co and Tb as well as an asymmetric spin current absorption accounts for the SOT switching mechanism. Our findings would advance the use of magnetic materials with bulk PMA for energy-efficient and thermal-stable non-volatile

Magnetotransport is at the center of spintronics. Mn3Sn single crystals, an antiferromagnet that has a noncollinear 120° spin order, exhibit large anomalous Hall effect (AHE) at room temperature. But such a behavior has remained elusive in epitaxial Mn3Sn films. Here the observation of AHE‐like behavior with in‐plane magnetic field up to room temperature in quasi‐epitaxial Mn3Sn thin films, prepared by magnetron sputtering, is reported. The growth of both (1120)‐ and (0001)‐oriented Mn3Sn films provides a unique opportunity for comparing AHE‐like behavior in three different measurement configurations. When the magnetic field is swept along (0001) plane, such as the direction of [0110] and [2110], the films show comparatively higher Hall conductivity than its perpendicular counterpart [0001], irrespective of their respectively orthogonal current along [0001] or [0110]. A quite weak ferromagnetic moment of ≈3 emu cm−3 is obtained in (1120)‐oriented Mn3Sn films, guaranteeing the switching of the Hall signals with magnetization reversal. This finding would advance the integration of Mn3Sn in antiferromagnetic spintronics.

A perpendicularly magnetized synthetic antiferromagnetic structure is a promising alternative to a single ferromagnetic layer in spintronic applications because of its low net magnetization and high thermal stability. In general, the reversal sequences of the two ferromagnetic layers in the structure are fixed for a specific sample since they have different magnetic anisotropy. Here, we investigate the anomalous Hall effect of the [Pd/Co]/Ru/[Co/Pd] synthetic antiferromagnetic structure. By rotating the external field from out-of-plane to in-plane, three different types of anomalous Hall effect curves can be observed, which shows obvious magnetic field direction dependent magnetization reversal behavior. The mechanism can be explained with the help of the Stoner-Wohlfarth model calculation, and the result indicates that the competition among Zeeman, anisotropy, and exchange coupling energies in the system is sensitive to the magnetic field direction, which changes the switching sequences. Besides the fundamental significance, our finding provides a different dimension to manipulate the performance of spintronics.