Geometric and anisotropy effects on voltage driven magnetic switching behaviors in nanoscale multiferroic heterostructure

Voltage driven magnetic switching (VDMS) in multiferroic heterostructure is highly demanded for next generation energy efficient high-density memory (e.g. magnetoelectric random access memory) and spintronic devices. For practical applications in large scale integrated device, it is imperative to understand the VDMS behaviors in nanometer scale. In this work, we have investigated the effects of geometric and anisotropy parameters on 180° VDMS behaviors in a model multiferroic heterostructure system consisting of Co nano-ellipse on BiFeO3 films by using micromagnetic simulation. It was revealed that the switching behaviors can be greatly affected by geometric factors, whereby dimension shrinkage and rising aspect ratio of Co nano-ellipse can apparently increase the critical exchange coupling field (hDMcri-field) needed for triggering the VDMS, greatly reducing the watchability of VDMS. To improve the watchability, an external static perpendicular magnetoanisotropy (Kp) can be introduced to reduce the hDMcri-field, whereas too large Kp tends to reorientate the magnetization towards out-of-plane orientation. Moreover, a strategy was also proposed to assist the VDMS by applying an anisotropy pulse, which is able to reduce the hDMcri-field and expand the switching window (e.g. wider range of aspect ratio and overall dimension size) for both in-plane and out-of-plane VDMS. These results may provide some guides for further experimental modulation of VDMS for device applications