摘要:

Experimental measurements have shown that nondestructive magneto‐optic readout from magnetic film computer elements by means of the longitudinal Kerr‐effect can operate at rates of at least one million bits per second. If the steady light source of the magneto‐optic apparatus is sufficiently bright, a signal‐to‐noise ratio of four or better can be obtained from the photomultiplier readout tube. Since the reversal time of thin ferromagnetic films is less than a microsecond, writing speed can be as fast as readout. Information readout from a magnetic film can be obtained by scanning with a high‐intensity light spot. Spurious variations in surface reflectivity of the films are sufficiently small so that parts of the film magnetized in opposite directions can be clearly determined. Experiments with an electronic strobing magneto‐optic method make it possible to observe the details of the magnetization reversal process in very small parts of a film with a time resolution of the order of a nanosecond. Since this strobing process involves sampling and integration, the information bandwidth is too small to be used for digital computer readout. However, this method is useful in studying fine details of the magnetization reversal process. Measurements show that the reversal is repeatable in the different parts of the film.

ISSN:0021-8979    

DOI:10.1063/1.1728598

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Structures formed by depositing different ferromagnetic thin metal films in direct contact with each other were found to display a square hysteresis loop without the step discontinuity usually associated with gross heterogeneous magnetic composites. The high‐speed switching characteristics of a bilayer structure composed of an electroplated 97 Fe‐3 Ni layer in contact with a uniaxially oriented 79 Ni‐21 Fe electroplate were intensively investigated. The switching characteristics of the bilayer were compatible with a nucleation and growth mechanism.

ISSN:0021-8979    

DOI:10.1063/1.1728599

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

This paper discusses some magnetostatic interactions between two thin films that are separated by a small distance between parallel film planes. The external field of a domain wall in one film is calculated using a simple wall model, and the effect of this field on a second adjacent film is determined. The conditions are investigated under which the wall field of the first film together with an external field can cause nucleation of a domain in the second film. The interaction energy between a movable wall in one film and a stationary wall or a linear imperfection in a second adjacent film is calculated using simple models. The equilibrium position of the movable wall as a function of an externally applied field is then determined. Means for electrically modifying the degree of interaction are investigated. Experimental results are presented illustrating the aforementioned interactions. The nucleation of long narrow domains in one film is achieved by the use of a domain wall, a scratch imperfection, or a film edge in a second adjacent film. The influence of a stationary wall in one film on the controlled wall motion of a wall in a second film is demonstrated. A comparison of theory and experiment is made. Mention is made of how the subject interactions might be utilized in new information storage devices.

ISSN:0021-8979    

DOI:10.1063/1.1728600

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

Annealed molybdenum Permalloy sheets of ⅛−1 mil thickness have been photoetched to form transfluxor‐element memory arrays utilizing inhibited‐flux storage. Operating characteristics are summarized for single elements switched in 21 nsec−3.2 &mgr;sec. Some findings are:onetozeroinformation flux ratios of 5:1 to 16:1,onetodisturb noiseflux ratios greater than 30:1, andSwvalues of 1.7 to 0.14 oe &mgr;sec. In addition, operation is possible over a temperature range of −70° to +150°C without drive‐current compensation. Also, for a ⅛‐mil thick element switched in times less than 0.1 &mgr;sec,Swvalues less than 0.2 oe &mgr;sec are obtained, indicating that fast switching may occur partially by uniform flux rotation. Array photoetching is described. Arrays containing 128 and 1152 elements have been fabricated. The latter permit a storage density of 250 000 bits/cu in. to be attained. The arrays receive a stress‐relief treatment which results in a signal uniformity of ±3%. Photofabrication of windings has been accomplished also. This process generates continuous windings linking the transfluxor apertures.

ISSN:0021-8979    

DOI:10.1063/1.1728601

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

The operations of read‐in, shifting, conditional erase, and fan‐out in a system of domain‐wall storage and logic proposed by Smith have been experimentally demonstrated. The several operations were performed by controlling the current flowing through a configuration of wires placed closely under a 5 to 40 mil wide, 50 to 300 A thick Permalloy strip, and the sequence of events was observed on the top side of the film using the Bitter technique. The basic wiring geometry was a narrow‐spaced grid of series‐connected parallel wires that made an angle of 50° to 75° with the strip of film, the smaller angles being necessary for the thinner films. Conditional erase was most successful in films below 100 A thick, as in this thickness range walls of the same sense form double walls which require relatively large fields for erasure.

ISSN:0021-8979    

DOI:10.1063/1.1728602

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

It is known that flux reversal in ferrites involves three switching mechanisms, namely, domain wall motion, nonuniform rotation, and uniform rotation. The experimental results presented in this paper demonstrate that a steady transverse field in conjunction with set and reset pulses is capable of separating these mechanisms into three regions of flux dispersion. Each region is designated by flux components &phgr;1, &phgr;2, and &phgr;3with corresponding characteristic transverse fieldsH1,H2, andH3. The output waveform of the longitudinal sense signal during flux reversal is characterized by its first peak, second peak, and the long tail. The 50% value of the second peak occurs at the same characteristic transverse fieldH2. The transverse field has no appreciable effect on their distribution. The experimental results agree with theoretical predictions in which less flux is switched by domain wall motion at higher drive currents. Furthermore, a proper transverse field has the effect of speeding up the switching time of a ferrite core without sacrificing the amplitude of the output signal due to the fast reversal mechanisms.

ISSN:0021-8979    

DOI:10.1063/1.1728603

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A complete solution of the modified Landau‐Lifshitz equation of magnetization reversal by coherent rotation is presented for &agr;2≫Ha/4&pgr;Ms, where &agr; is the phenomenological damping constant,Hais the applied field, andMsis the saturation magnetization. This solution extends previous work in that it is valid fort≥0, whereas, other solutions have not been valid over this entire range. In addition, from this solution the time dependence of the demagnetizing field is found.

ISSN:0021-8979    

DOI:10.1063/1.1728604

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

An element for performing digital logic which employs Permalloy wire, solenoids, and resistors and utilizes a two‐phase current pulse source has been studied experimentally. The reentrant hysteresis loop exhibited by a torsionally strained Permalloy wire provides the mechanism for power gain. A balanced input circuit assures unidirectional information flow and provides means for obtaining logic functions. Each element consists of two 0.6‐in. bifilar‐wound solenoids for bias and reset pulse currents, one or several 0.025‐in. solenoids to which logic inputs are applied, an output resistor and a Permalloy wire core. The application of a bias current pulse to the logic element will cause the magnetization to change from thezeroto theonestate provided a signal is present simultaneously at the input to nucleate the magnetization reversal. The reset current pulse switches the magnetization back again and produces an output across the bias coil which is used to control one or several following elements. A buffer zone, the magnetization of which is controlled by the reset pulse, separates adjacent logic elements to minimize element interaction. Measurements on elements employing a 1.5‐mil, 5–79 Permalloy core show that a switching time of 15 &mgr;sec and a power gain of 10 can be achieved. Preliminary tests indicate satisfactory operation over the temperature range of −55° to +185°C. These elements have been used to construct flip‐flops, binary counters and a serial adder which employs majority logic. The circuits operated successfully when the pulse currents from the power supply were varied by ±20%. Because an open flux structure is used, it is believed that similar techniques will have application in circuits employing deposited magnetic films.

ISSN:0021-8979    

DOI:10.1063/1.1728605

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

A card changeable permanent magnet twistor memory element of improved characteristics has been designed. The desired characteristics were obtained by:(1) Halving the solenoid width to enhance the drive field.(2) Replacing the copper return wire in the twistor pair with a reverse wrapped twistor wire.(3) Installing a Permalloy sheet between the word solenoid and the solenoid board to reduce interaction fields within the memory.(4) Annealing the twistor wire to lower the coercive force and to increase the squareness ratio of the moly‐Permalloy tape.The chief result of these changes is that the net switching field at the bit is substantially increased and therefore the outputs of the memory are less dependent on the properties of the magnetic materials.A 210 000 bit card changeable permanent magnet twistor memory utilizing the new element design has been constructed and evaluated.In comparison to previously reported permanent magnet twistor memories, the new design is characterized by twice the speed, 2.5 times the bit density, 3 times the output voltage level, 2.5 times the signal available for ``1–0'' discrimination, and 4 times the strobe time tolerance.

ISSN:0021-8979    

DOI:10.1063/1.1728606

出版商:AIP    

年代:1962

数据来源: AIP

摘要:

This paper describes effects of anisotropy of the hyperfine interaction on nuclear magnetic resonance in a ferromagnetic or ferrimagnetic material. It is shown how the line shape in a polycrystalline sample depends on whether the excitation is through domains or domain walls. The absorption spectrum of Fe57in powdered magnetite (Fe3O4) is observed, and the results show that, in this case, the excitation is predominantly through domains. They also establish a value for the hyperfine anisotropy on octahedral sites.

ISSN:0021-8979    

DOI:10.1063/1.1728607

出版商:AIP    

年代:1962

数据来源: AIP