Electrically driven magnetic switching (EDMS) is highly demanded for next-generation advanced memories or spintronic devices. The key challenge is to achieve repeatable and reversible EDMS at sufficiently small scale. In this work, we reported an experimental realization of room-temperature, electrically driven, reversible, and robust 120° magnetic state rotation in nanoscale multiferroic heterostructures consisting of a triangular Co nanomagnet array on tetragonal BiFeO films, which can be directly monitored by magnetic force microscope (MFM) imaging. The observed reversible magnetic switching in an individual nanomagnet can be triggered by a small electric pulse within 10 V with an ultrashort time of ∼10 ns, which also demonstrates sufficient switching cycling and months-long retention lifetime. A mechanism based on synergic effects of interfacial strain and exchange coupling plus shape anisotropy was also proposed, which was also verified by micromagnetic simulations. Our results create an avenue to engineer the nanoscale EDMS for low-power-consumption, high-density, nonvolatile magnetoelectric memories and beyond.

Ferroelectric topological objects provide a fertile ground for exploring emerging physical properties that could potentially be utilized in future nanoelectronic devices. Here, we demonstrate quasi-one-dimensional metallic high conduction channels associated with the topological cores of quadrant vortex domain and center domain (monopole-like) states confined in high quality BiFeO3 nanoislands, abbreviated as the vortex core and the center core. We unveil via the phase-field simulation that the superfine metallic conduction channels along the center cores arise from the screening charge carriers confined at the core region, whereas the high conductance of vortex cores results from a field-induced twisted state. These conducting channels can be reversibly created and deleted by manipulating the two topological states via electric field, leading to an apparent electroresistance effect with an on/off ratio higher than 103. These results open up the possibility of utilizing these functional one-dimensional topological objects in high-density nanoelectronic devices, e.g. nonvolatile memory.

The discovery and precise manipulation of atomic‐size conductive ferroelectric domain walls offers new opportunities for a wide range of prospective electronic devices, and the emerging field of walltronics. Herein, a highly stable and fatigue‐resistant nonvolatile memory device is demonstrated, which is based on deterministic creation and erasure of conductive domain walls that are geometrically confined in a topological domain structure. By introducing a pair of delicately designed coaxial electrodes onto the epitaxial BiFeO3 film, a center‐type quadrant topological domain with conductive charged domain walls can be easily created. More importantly, reversible switching of the quadrant domain between the convergent state with highly conductive confined walls and the divergent state with insulating confined walls can be realized, resulting in an apparent resistance change with a large on/off ratio of >104 and a technically preferred readout current (up to 40 nA). Owing to restrictions from the clamped quadrant ferroelastic domain, the device exhibits excellent restoration repeatability over 108 cycles and a long retention of over 12 days (>106 s). These results provide a new pathway toward high‐performance ferroelectric‐domain‐wall memory, which may spur extensive interest in exploring the immense potential in the emerging field of walltronics.

In the past decade, a series of breakthrough discoveries in new exotic polar topological states have been witnessed, e.g., vortex, skyrmion, and meron. These tantalizing findings open a new avenue toward a plethora of emerging physical phenomena and offer opportunities for a wide range of future configurable electronic devices, which might eventually lead to an exciting area, the so-called “topotronics.” Although this field has seen a rapid progress, especially in revealing various novel topological states, the associated emerging phenomena and functionalities as well as application potentials yet remain largely unexplored, which might become fruitful areas in the upcoming years and thus deserve more attention. In this perspective, we give a brief overview on the recent advances in the field of exotic polar topological states, highlighting the emerging phenomena and efforts to control these functional topological objects. Finally, we present a concluding summary with some suggestions for future directions.

Conductive ferroelectric domain walls-ultranarrow configurable conduction paths-have been considered as essential building blocks for future programmable domain wall electronics. For applications in high-density devices, it is imperative to explore the conductive domain walls in small confined systems, while earlier investigations have hitherto focused on thin films or bulk single. Here, an observation and manipulation of conductive domain walls confined within small BiFeO 3 nanoislands aligned in highdensity arrays are demonstrated. Using conductive atomic force microscopy, various types of conductive domain walls, including the head-to-head charged domain walls (CDWs), zigzag domain walls, and typical 71° head-totail neutral domain walls (NDWs), are distinctly visualized. The CDWs exhibit remarkably enhanced metallic conductivity with current of ≈nA order in magnitude and 10 4 times larger than that inside domains (0.01-0.1 pA), while the semiconducting NDWs allow much smaller current (≈10 pA) than the CDWs. The substantial difference in conductivity for dissimilar walls enables manipulations of various wall conduction states for individual addressable nanoislands via electrical tuning of domain structures. A controllable writing of four distinctive states in individual nanoislands can be achieved, showing application potentials for developing multilevel high-density memories.