Method of making a magnetic head

A method of making magnetic head core pieces for use in making a magnetic gap formed by cementing together a pair of magnetic head core pieces at least one of which has the face within the joint coated with glass, said method comprising:

• depositing a glass layer on a surface of a magnetic head core piece made of a magnetic head core material by a cathodic sputtering of a glass target means by mounting said piece in a sample holder and, while carrying out said sputtering, rotating the sample holder around the target means with the surface of said piece facing in a direction lateral to the target means;
• positioning a mask plate between said target means and the circumferential path of said piece for preventing an excess of sputtered glass from being deposited onto said piece;
• and monitoring the thickness of the sputtered glass layer formed on said piece by directing a light beam of a wavelength .lambda. directly onto said surface of said piece in a direction for producing an interference light beam reflected from said piece, the speed of rotation of said sample holder being at least 50 .sup.V dep/n.lambda. , in which .sup.V dep is the speed of deposition of the sputtered glass per minute and n is the refractive index of the deposited glass layer, whereby the intensity of the interference light beam is indicative of the thickness of the sputtered glass layer.