Bias Margin Research Articles

Field access bubble-to-bubble logic operations

Bubble-to-bubble logic operations can greatly enhance the versatility of bubble memory devices. Our experience to date, however, has shown us that logic operations reduce the device operating margins to a degree that would allow logic only where the ratio of memory sites to logic gates is greater than one hundred. For example, quasistatic rotating field operation of exclusive OR, AND/OR, and replicate gates was obtained for a ± 3.5 percent bias margin at 45 to 55 Oe rotating field drive for an AND/OR gate to a ± 1.5 percent bias field margin at 50 to 60 Oe rotating field drive for an exclusive OR gate. In all cases these devices were prepared by ion milling or chemical etching T-bar, Y-bar, or chevron patterns in 3000 to 5000 A thick Permalloy films on glass. The pattern feature sizes ranged from 3 to 7.5 μm. The Permalloy on glass patterns were placed on epitaxially grown magnetic garnet wafers with bubble diameters ranging from 8 to 17 μm. Circuit operation was determined by visual observation. In all cases, the results are from either the first design of the circuits or the first iteration design.

Functional speed measurements of propagating devices utilizing cylindrical domains in orthoferrites and garnets

Functional speed, measurements have been made on field-access T-bar and Y-bar bubble devices utilizing flux-grown crystal platelets of Gd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2.34</inf> Tb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.66</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> , Eu <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> Er <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.65</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4.35</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> , Sm <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.55</inf> Tb <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.45</inf> FeO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> , and epitaxially grown films of Eu <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</inf> Er <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.7</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4.3</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> . Propagation rates of 250 kbit/s with bias margins of ±7 percent have been achieved with epitaxial garnet films. A propagating device utilizing an epitaxial garnet film has demonstrated a storage capability of 1.6 Mbit/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> .The device, Which includes a propagation turn, has been worse case tested. This resulted in a bias margin of ±7 percent with a 25-Oe 100-kHz rotating in-plane field.