Robert F. Elfant

An approach towards batch fabricated ferrite memory planes

This paper describes a technique for the batch fabrication of ferrite memory arrays in which wire, previously coated with a thermoplastic, is formed into two orthogonally disposed sets of parallel wires. These grids are oriented between opposingm olds having matched grooves filled with a fluid mixture of ferrite powder and thermosetting resin, in such a manner that one set of parallel wires coincides with the groove axes. After suitable curing this structure is released and heat treated to pyrolyze the organic materials and sinter the ferrite. A yield study on 108 memory arrays produced in this manner resulted in a yield of 72.2% on pulse testing under simulated operating conditions and an over-all process yield of 36.1%. The paper concludes with a tabulation of electrical characteristics of the arrays and a brief discussion of the applicability of the technology to various modes of operation and its potential for high-speed (250 nsec magnetic cycle time) operation.

Direct Observation of Rotational Switching in Polycrystalline Ferrite Materials

The high‐field switching mechanism of polycrystalline ferrite material is investigated. Direct experimental evidence for rotational switching is obtained by observing the charges in the longitudinal and transverse components of the magnetization, for a long (L=1.33 cm), thin‐walled (o.d.=0.05 cm, i.d.=0.028 cm) ferrite tube, during the reversal process. For a 10‐Oe circumferential pulse field in the presence of a 4.3‐Oe longitudinal bias field, it is found that at least 30% of the total magnetization reverses by a rotational process.

Approximate Solution of the Equations of Magnetization Reversal by Coherent Rotation

A complete solution of the modified Landau-Lifshitz equation of magnetization reversal by coherent rotation is presented for α2≫H a/4πM s, where α is the phenomenological damping constant, H a is the applied field, and M s is the saturation magnetization. This solution extends previous work in that it is valid for t≥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.