Magnetization reversal in asymmetric trilayer dots: effect of the interlayer magnetostatic coupling

Abstract

The spin structure and magnetization reversal in Co/insulator/Fe trilayer nanodots are investigated by micromagnetic simulations. The vortex and C-state are found and the magnetization reversal is dominated by the shape asymmetry of the dots, which is produced by cutting off a fraction of the circular dot. The vortex chirality is thus controlled by the magnetic field direction. On the other hand, the magnetostatic interaction between the top and bottom magnetic layers has interesting influence on the dot reversal process, where the magnetocrystalline anisotropy direction of the Co layer is allowed to vary within the layer plane. The combined effect of these two aspects is discussed on the base of dot coercivity, remanent magnetization, vortex nucleation and annihilation, and the bias of the Fe layer hysteresis loop. While leading to a new S-state in circle dots, the interlayer interaction facilitates the formation of C-state in asymmetric dots, which reduces the vortex nucleation field. The bias effect of all dots is decreased with the deviation of the Co layer easy axis from the field direction. Unlike the circle and semicircle dots, the field range of the vortex state in other asymmetric dots increases with the angle between the cutting direction and the Co layer anisotropy. Additionally, vortex ranges in less asymmetric dots even larger than that in the circle dots are evidenced unexpectedly. Therefore, the control of the vortex chirality and enhancement of the vortex range are found simultaneously.

A skyrmion-based non-volatile racetrack with a potential well structure

“…The depth of the potential well decreases with the increase in the thickness of the non-magnetic layer. This has been proved in many experiments [36,40]. Increasing the thickness of the Co ring can significantly increase the depth of the potential well, as shown in figure 2(d).…”

“…Magnetostatic interaction has been demonstrated for multilayer systems with insulating layers in the middle. The energy does change when the skyrmions move on the multilayer because of the magnetostatic interaction [34,40]. Here, we use one code position to explain the energy potential well in our model.…”

“…The signal transmission is realized by applying in-plane current pulses periodically. This structure uses the magnetostatic interaction between the Co layer and Co rings to form code positions at the positions of the Co rings [40]. With both bit '1' and '0', each code can be stored in a code position; this ensures that the signals are in order and cannot be lost.…”

Applications of nanomagnets as dynamical systems: I

“…Furthermore, the switching field distribution or SFD of the dot array became broader with a decrease in dot size (figure 9(e)). By performing micromagnetic simulations, Yan et al investigated magnetization reversal in Co/insulator/Fe tri-layer dots with asymmetric shape, where shape anisotropy was induced by slicing away a section of the circular dot [121]. It was found that when the induced shape anisotropy is varied, the reversal field varies significantly owing to the modification of the domain formation process during magnetization reversal.…”

Applications of nanomagnets as dynamical systems: II

“…It was observed that the patterning process severely damaged the magnetic layer resulting in a decrease of the switching field and an increase in the switching field distribution (SFD) of the dot array with decreasing dot size (figure 6 (e)). By performing micromagnetic simulations, Yan et al investigated magnetization reversal in Co/insulator/Fe tri-layer dots with asymmetric shape, where shape anisotropy was induced by cutting a section of the circular dot [102].…”