Switching of Asymmetric Bloch wall in a ferromagnetic rectangular disk

Abstract

In a submicron-scaled patterned ferromagnetic thin film, magnetic domain walls (DWs) appear to reduce overall free energy in magnetic films, and they have been identified two types of DWs : In thin and patterned film Neel type domain wall is energetically favored where the spin rotates within plane, and the thicker films have Bloch type domain wall where spins tilt through out-of-plane alignment.[1-4] Such magnetic configurations mainly focused on controlling, manipulating and moving their internal magnetic configuration to develop next generation spintronic devices. In a relatively thick disk, an asymmetric Bloch wall (ABW) with Néel cap forms between two vortex cores to minimize the demagnetization energy along the thickness direction. In this system, there are two degenerate states of ABWs whose rotating orientation is clockwise (CW) or counter-clockwise (CCW) and they are exactly same energy states, they can appear at the same probability within one wall. To switch those states, it is necessary to break the symmetry of two states. For example, asymmetric geometry was utilized for control the ABW states [5]. In this presentation, we propose an efficient way to switch the rotating orientation based on the symmetry breaking of the ABW through the external magnetic field the using micromagnetic simulation and magnetic transmission soft X-ray microscopy, we have observed the switched ABWs in a 100nm thick, rectangular patterned thin permalloy film.