Method of manufacturing ferrimagnetic material for recording, read out and erase heads utilized in magnetic layer devices

#The present invention relates to a ferrimagnetic material of the ferrite type, highly suited to the manufacture of recording, read-out and erase heads or head assemblies, for magnetic memories. The memories concerned here are in particular, tape stores, disc stores or drum stores in which the magnetic film is deposited upon a substrate moving beneath the head or multihead system.

#The head essentially comprises a magnetic circuit containing an air-gap and at least one winding (of conductor wire) having a multiple function (write-in, read-out, erasing.) Each function may be performed by a special head. Currently, the air gaps are in the order of one micron and the distance between head and magnetic film is in the same order of magnitude.

#In order, under these conditions, to achieve efficient performance of the difficult functions, the magnetic circuit must be made using a material which satisfies the following requirements:

#The invention will be better understood and other of its features rendered apparent, from a consideration of the ensuing description and the attached drawings in which:

#FIG. 1 is a graph of three electrical or magnetic characteristics relating to an example of a material in accordance with the invention when the parameter e in the general chemical formula is varied.

#FIGS. 2 to 4 are graphs illustrating the real and imaginary components of the complex magnetic permeability, as a function of frequency, for three examples of materials in accordance with the invention.

#The various quantities and parameters being relatively numerous in the following discussion, it has been decided to make an alphabetical list of them at this point:

#magnetisation per gramme "s" (magnetisation density in CGS units);

#coercive field strength in Gauss (H.sub.c);