Improvements relating to magnetic thin film elements for magnetic stores

摘要

A magnetic thin film element suitable for use in a magnetic store of the kind disclosed in Specification 1,045,572 comprises alternate layers of magnetizable material one having positive magnetostriction, the other having negative magnetostriction, and each being less than 2000A DEG thick. In particular the films are of NiFe alloy, those with positive magnetostriction having slightly less than 82% nickel, and those with negative magnetostriction having more than 82% nickel. The layers are deposited in grooves to give an element having an overall negative magnetostriction and a square hysteresis loop. In preparation two electro-plating baths are prepared, the first for negative magnetostriction comprising NiSO4, NaCl, boric acid, sodium lauryl sulphate and sodium saccharin, and the second for positie magnetostriction comprising this with the addition of ferrous ammonium sulphate. A grooved substrate is immersed in bath 1 with the groove at 22 1/2 DEG to an applied magnetic field, and plated for 15 seconds at 8mA/sq. cm. It is transferred to the second bath, again in the magnetic field, plated for 2 minutes at 2mA/sq. cm. and rinsed. The process is repeated 12 times giving an overall thickness of 10000A DEG -14000A DEG . Reference has been directed by the Comptroller to Specification 925,766.