The annihilation of vertical-Bloch lines in the walls of hard domains to which bias fields and in-plane fields are alternately applied

The annihilation of vertical-Bloch lines in magnetic domain walls of the or dinary hard bubbles, to which both bias fields and in-plane fields are alte rnately applied, is investigated experimentally. The influence of an in-pla ne magnetic field on ordinary hard bubbles (OHB), dumbbell domains of the f irst kind (ID), and dumbbell domains of the second kind (IID) was analyzed, and a critical in-plane field range [H-ip(0),H-ip(2)] for vertical Bloch l ine (VBL) annihilation was found. For the three types of hard domains (H-ip (0) is the minimum critical in-plane field of VBLs which begin to be unstab le, H-ip(2) is the minimum critical in-plane field which only needs to be a pplied one time for collapse of all OHBs), the critical field range is the same with H-ip(0) = 8 piM(s). We hypothesize that there exists a direction along which the vertical-Bloch lines in the domain walls are annihilated mo st easily. It is also observed that the stability of vertical-Bloch lines i n the domain walls does not depend on the initial state. This provides a mo re detailed description of the minimum critical in-plane field than previou sly known. (C) 2001 Elsevier Science B.V. All rights reserved.