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    1.
    发明专利
    未知

    公开(公告)号：DE1271187B

    公开(公告)日：1968-06-27

    申请号：DE1271187

    申请日：1965-03-12

    Applicant: IBM

    Inventor： MIDDELHOEK DR SIMON

    IPC: G11C7/02 ,  G11C11/14 ,  G11C11/15 ,  H01F10/30 ,  G11B5/64

    Abstract: 1,095,431. Magnetic storage devices. INTER NATIONAL BUSINESS MACHINES CORPORATION. Feb. 17, 1965 [April 3, 1964], No. 6752/65. Heading H1T. [Also in Division H3] In a magnetic thin film store creeping of the domain walls due to stray fields acting on the elements in the hard direction is effected by preventing Bloch lines forming in the storage elements. In the memory shown in Fig. 1 information is written into the thin film stores 13, 14, 23, 24 by passing a word pulse to the appropriate word line 1, 2 so that the magnetization below that word line is deflected into the hard direction and simultaneously passing a bit pulse having the appropriate polarity along a selected one of the bit lines 3, 4 from amplifiers 30, 40. To read-out a stored bit a word pulse is passed along the selected word line and the bit lines connected to sense amplifiers 35, 45 the polarity of the voltage induced in the bit line determining the bit stored. Information is written back into the store after read-out or by limiting the strength of the word field non- destructive read-out may be performed. When pulses are applied to the word lines stray fields also act on the thin elements other than those directly beneath the energized line, the stray fields acting in the hard axis of these films. The effect of an alternating or repeated field in the hard axis on a thin film in which the domains are separated by cross-tie walls is for the Bloch lines to move back and forth in the walls, Figs. 5a and 5b (not shown). This results in a lowering of the stability of the domain walls and a consequent switching of the films due to stray fields. It is shown that Bloch lines disappear either with decreasing film thickness, i.e. the cross tie walls become pure Neel walls or with increasing film thickness, i.e. pure Bloch walls. It is also shown that if the magnetization above and below the domain wall is not orientated purely antiparallel for example when an external field is applied parallel to the hard direction then at certain angles of the vectors a change in the structure of the domain wall can occur, Fig. 7 (not shown). This is made use of in a second embodiment wherein a constant bias field acting on all the cells at a direction such that the rest position of the magnetization vector is at an angle of 25 degrees with the easy axis is applied. This enables films of up to 1000 Š in thickness to be used to achieve creep free operation. Alternatively it is shown that under certain conditions the occurrence of Bloch lines can be prevented in magnetic double films of which each individual film has a thickness of 400 Š. The films are separated by a layer of non-magnetic material such as silicon monoxide, Fig. 8. In this case Neel walls form rather than cross-tie walls.

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