Browse Prior Art Database

Information Store Using Soft Magnetic Bubbles

IP.com Disclosure Number: IPCOM000084158D
Original Publication Date: 1975-Sep-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 4 page(s) / 51K

Publishing Venue

IBM

Related People

Hendel, RJ: AUTHOR [+3]

Abstract

Information states are represented by different states of the domain wall structure in the magnetic bubble, using horizontal Bloch lines. Encoding is achieved by using domains having different vertical twist numbers, or having different signs of vertical twist. Writing is achieved by using a vertical-gradient field, while reading is accomplished by detection of bubble inertia. Writing.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 38% of the total text.

Page 1 of 4

Information Store Using Soft Magnetic Bubbles

Information states are represented by different states of the domain wall structure in the magnetic bubble, using horizontal Bloch lines. Encoding is achieved by using domains having different vertical twist numbers, or having different signs of vertical twist. Writing is achieved by using a vertical-gradient field, while reading is accomplished by detection of bubble inertia. Writing.

To encode the bubble, it is transported by known means to a position under the edge of a conducting strip line, as shown in Fig. 1. An alternative is to place it under a hairpin loop as shown in Fig. 2.

Next, n (= 0 to 20) pulses of current I are applied to the conductor. The resultant applied-field distribution is not uniform, as indicated in the side views of Figs. 1 and 2. Particularly, the vertical component H(z) is greater at the top point A of the domain wall than at the bottom B.

A section of the domain wall structure is shown enlarged in Fig. 3. A general feature of the wall structure is the static pinning of the wall moment along a direction normal to the wall plane and parallel to the film surface, at points just within the film surfaces. The wall moment has w + 1/2 continuous twists between the two surfaces. Here w is an integer (positive or negative), considered to represent an information state. When absolute value of w is large, the bubble may be regarded as "soft" as explained below.

The effect of the pulse sequence described above is to change w, the sign of the change depending on the sign of the current. The change in twist arises from the differential precession of the wall moment arising from the vertical gradient in the field distribution. A mean field amplitude of H = 7 oersted and pulse length of 1-10 mu sec are adequate. Varying the amplitude, sign, number and length of pulses provides the writing function. Reading Several methods of reading are available. Collapse reading.

According to theory, the static collapse field decreases by 8A D/-1/h/-1/(2 pi/K)/1/2/ for each additional twist in the wall moment. Here A = exchange stiffness (~ 2.5 x 10/-7/erg/cm), D = bubble diameter (~ 5 x 10/-4/ cm), h = film thickness (~ 5 x 10/-4/ cm), and K = uniaxial anisotropy (~ 10/4/erg/cm/3/). For the typical material parameters given, this amounts to 0.4 oersted per winding collapse-field reduction. (Hence the term "soft" bubble.)

Changes of up to 7 oersted have been observed after 20 writing pulses of one sign. Thus, different values of absolute value of w + 1/2 may be employed for "0" and "1". The static field H , produced by, say, a current loop is adjusted to a value sufficient to collapse the 0 but not the 1. If a bubble survives, it may be expanded and detected by conventional means, registering a 1. Inertial reading.

According to Schloemann's theory (J. Appl. Phys., 1974), the twisted wall ("anomalous" wall) mass m is 100 or more times greater than the untwisted wall (w + 1/2 = + or - 1/2...