Maynard C. Paul

Transverse recording using thin film recording heads

This paper presents the results of an investigation of a high density magnetic recording technique utilizing a thin film recording head and a transverse mode of recording on thin media. The significant results of this investigation are as follows. 1) Densities as high as 18 500 transitions per inch were experimentally written in a 300-A thick FeCr medium having an H c of 70 oersteds. 2) These densities were written with a thin film, vapor-deposited, recording head having a MATED-FILM® structure with a 0.4-mil etched gap. 3) Track widths of 1-mil on 2-mil centers were experimentally achieved. 4) Optical readout of a 0.2-mil wide transition (width of beam) region corresponding to 5000 transitions per inch was achieved using a laser beam and a linear motion transport system under ideal experimental conditions. 5) The magnetic field from the Neel wall separating recording domains was detected using a MATED-FILM Etched Gap head making this a possible readout method. Maximum achieved linear bit densities as a function of recording media coercivities are given.

A Y-domain magnetic thin film memory element

A memory element using Y-shaped domain wall structures in Ni-Fe films to represent data bits is presented. The memory element geometry, fabrication conditions, magnetization characteristics, and principle of operation are described. A 50-ns coincident current write and a 250-ns nondestructive read are described.

Vapor-deposited thin-film recording heads

A vapor-deposited thin-film recording head and a unique reading technique are described. The head structure used for both write and read is similar to that of the Mated-Film memory element. Conventional longitudinal recordings at 4000 flux reversals per inch have been written with a thin-film head in 300-A-thick iron films having a coercivity of 80 Oe. Conventional longitudinal recordings up to 1600 flux reversals per inch in thin-film media and in oxide media have been sensed with the thin-film head. Although a one-turn sense line is used, flux amplification is obtained because the head magnetization, not the flux from the recording, is sensed. This also results in an output signal that is independent of recording media velocity.

Geometry of serrated magnetic film strips for the cross-tie memory

A method of utilizing edge demagnetizing effects for placing data tracks (i,e. cross-tie walls) for a serially accessed crosstie memory is described. Lorentz micrographs show results using a proposed, rounded and slightly asymmetrical, edge geometry.

Mass filter studies of gases in a 90-liter getter-ion vacuum system

Abstract The basic residual gases present in a 90-liter titanium getter-ion vaccum system operating under different conditions are determined with the aid of a quadrupole-field mass filter. Mass spectra of gases in the system during successive temperature increases of molybdenum and tungsten filament heaters over a temperature range from 25°C to 1050°C for molybdenum and 25°C to 1250°C for tungsten are presented. Possible sources of the gases are discussed primarily in terms of outgassing characteristics of materials and interaction between gases and the surfaces on which they impinge. Fragments resulting from the introduction of solvents commonly used in cleaning vacuum hardware (acetone and isopropyl alcohol) are presented. Results show that major residual gases present in the getter-ion system are carbon monoxide, nitrogen, argon, hydrogen, methane, and water vapor, with their order of prominence variable depending upon conditions. The introduction of hot tungsten or molybdenum filament heaters does not alter the gas profile appreciably until their surface temperatures reach about 1000°C, at which point outgassing from surrounding surfaces becomes appreciable. Carbon dioxide, carbon, and a host of hydrocarbons then play increasingly important roles. When acetone and isopropyl alcohol are introduced into the vacuum system, they dissociate quite readily and completely into several smaller components, in particular CH+, CH3+, C2H3+, C2H5+, and C3H3+.

Domain Studies in Thin Film Recording

An observation technique utilizing the longitudinal Kerr magneto‐optic effect was used in various studies of thin film recording. The semitransparent nature of the recording media allowed simultaneous observation of recorded domains and the write and read head gaps. Thin film heads were used to record in iron films having coercivities ranging from 60 to 160 Oe. The apparatus allowed quick determinations of maximum linear densities which were as high as 1550 flux reversals/cm. Recorded domain orientation with respect to the gap of a thin film read head was easily observed, and the corresponding output signals on an oscilloscope were photographed. The write‐read‐observe apparatus with a thin film read head was also helpful in detecting the magnetic field from Neel walls.

Self-structured, current aperture approach for bubble memory

An approach to magnetic bubble memory which incorporates dual conductor current access drive with a self-structured (strongly interacting) bubble lattice is described. This is expected to provide higher operating speeds, defect tolerance, and higher bit density for a given bubble size as compared to present field access bubble devices. Bubble spacings of 2.5 bubble diameters are projected for a prototype device. Experimental work on device components including detectors, major/minor loops, and gates is described. Defect tolerance has also been demonstrated.