W. C. Hubbell

Magnetoresistive properties of a chevron stretcher detector

To better understand how bubbles affect a resistance change in a Permalloy chevron stretcher detector, a more detailed knowledge of the magnetoresistive properties of such elements in the absence of bubbles is required. Results of systematic resistance measurements on a single element as a function of magnitude, H, and direction of an inplane dc magnetic field are presented for 10 Oe

Operation of a bubble memory chip with a triangular drive field

This paper describes the complete operation of a 20 kbit major/minor loop memory chip with a 100 KHz triangular drive. Data are presented which compare the triangular drive with sinusoidal drive for operational characteristics such as bias field margin, longevity, bubble signal amplitude and control pulse tolerances. Chip operation with triangular drive compares favorably with sinusoidal drive although the power requirement is higher.

On the operation of a pickax replicate/transfer gate

The design of a pickax replicate/transfer gate has been reported.1 Here we report on the operation of this element with respect to variations in the current pulse parameters (amplitude A, width tw, and position tp), inplane drive field amplitude and bias field. This element was operated at 100 KHz on (YSm)3(FeGa)5O12 garnet with a nominal bubble diameter of 5 μm and was configured in the major loop to detector path on a major/minor loop chip. The following values of pulse parameters provide replicate and transfer bias field margins equal to that of loop propagation (16 Oe) while maintaining acceptable tolerances: Replicate: A=75 mA, tw=2.0 μsec and tp=5.4 μsec (zero μsec corresponds to the inplane field parallel to the long axis of the pickax element); Transfer: A=75 mA, tw=4.0 μsec and tp=3.8 μsec. With these pulse parameters, reducing the drive field amplitude from 40 to 25 Oe reduces the bias field margin for replicate and transfer by 3 and 2 Oe, respectively.

ω−2ω transition in a chevron stretcher detector

The ω−2ω transition1 in the magnetoresistance waveform at 100 KHz was investigated for a long Permalloy chevron stretcher detector in the absence of bubbles propagating through the structure. When the Permalloy is demagnetized by decreasing the rotating inplane field, H, in the absence of any dc fields, the waveform of the resistance variation is 2ω for 0<H<40 Oe, where ω is the angular frequency of rotation. When the Permalloy is ac demagnetized in the presence of a small dc field applied along the long axis of the detector element, the resulting waveform has an ω dependence for 0<H≲20 Oe, becoming 2ω for 20<H<40 Oe. In the ω regime, the phase angles of the rotating inplane field at which resistance maxima occur depend on the direction in which the dc field was applied during demagnetization. A domain model based on magnetization fanning is proposed to explain these results.