Abstract: In a magnetic memory device comprising a magnetic medium (21) having an easy axis of magnetization orthogonal to a principal surface of the medium, the medium has at least one stripe domain (20) surrounded by a domain wall which memorizes information in the form of a pair of vertical Bloch lines. Each pair is written in one end of the domain by supply of a local magnetic field to the one end when no magnetic bubble exists in the proximity of the one end. Each information is specified by absence or presence of each pair and successively transferred along the domain wall by a pulsed bias magnetic field. Readout operation is carried out at a preselected end of the stripe domain by supply of another local magnetic field to the preselected end to selectively chop the preselected end into a magnetic bubble only when each pair exists in the preselected end. Thus, presence and absence of each pair is converted into presence and absence of the bubble.

Abstract: A method for detecting the wall state of a soft bubble based upon the collapse characteristics of the bubble domain on a layer of bubble domain supporting material is described. The method includes the step of exchange coupling a magnetic layer, for example, an ion-implanted layer, to the bubble supporting layer. An in-plane field is applied to the bubble supporting layer when Bloch lines are present in the bubble domains. The bias field and the pulse field are set at a level to form a range of pulse widths which are suitable for the discrimination of soft bubble domains having different wall states. A pulse is then applied for a time sufficient to collapse only the S=1 bubble and not the S=0 bubble. Thereby this method distinguishes S=0 bubbles having one pair of winding Bloch lines from S=1 bubbles having one pair of unwinding Bloch lines. This method also distinguishes S=1 bubbles having a clockwise chirality from S=1 bubbles having a counterclockwise chirality.