In present day large computers the memory cycle is on the order of 8 μsec requiring memory cores to switch in 1.5 μsec with a full select drive of approximately 0.7 amp. Memory cores used in such a computer can be fabricated from a MgO·MnO·Fe2O3 ferrite material. Using the same ferrite material, memory cores have been developed which have a switching speed of 0.4 μsec with a full select drive of approximately 1.0 amp. The procedure used to develop these high-speed coincident current memory elements is described. The drive current is reduced to approximately 0.7 amp when partial substitutions of CaO and Cr2O3 are made for MgO and Fe2O3, respectively, in the MgO·MnO·Fe2O3 core composition.
Dielectric constant and tan δ of powdered crystal phases of alumina, quartz, and wollastonite were determined. Since it is very difficult to obtain dielectric measurements of very fine (powdered) crystals, a technique of embedding the solids in a homogeneous medium was used. The relationship between particle shape and volume present in the composite to the dielectric properties of such fine powders was in accord with that indicated by Niesel's theory.
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