Abstract: A magnetic erasing head for erasing a magnetic recording media such as magnetic tape. The device has a head surface defined to make sliding contact with the tape surface. The head surface includes a permanent magnet material and a high permeability material. The permanent magnet material defines the portion of the head surface extending from the inlet side toward the exit side thereof for the sliding tape and is magnetized to include portions which have alternate polarities and which have a field strength which gradually decrease from the inlet side to the exit side of the head surface. The high permeability material defines a portion of the head surface with a predetermined length from the exit side toward the inlet side and with a width of about one-half of the recording track of the tape. The high permeability material is positioned substantially in alignment with the center of the recording track.

Abstract: A speaker diaphragm of the present invention is prepared in a manner such that a boron layer is formed on one face of a dome-shaped metal foil by means of a physical vapor deposition method such as ion-plating, cathode sputtering, vacuum evaporation or the like, when necessary the metal foil is thinned by etching, and then, if necessary, another boron layer is formed on the other face of the metal foil. Alternatively, a metal layer is formed on the surface of the boron layer. The resultant speaker diaphragm is light in weight and high in modulus and also has appropriate internal mechanical resistance against vibration, thereby providing a speaker of high efficiency and satisfactory characteristics.

Abstract: A magnetic head having a high wear resistance and high workability such as by grinding, and a method for manufacturing the same. According to this method, at least a portion of that surface of the core forming the magnetic head or shielding case, which is to be brought into contact with a magnetic recording medium, is subjected to a boronizing treatment to form a boronized layer.

Abstract: A composite diaphragm for a speaker comprises a boron layer formed on a metal foil such as titanium foil, in which a layer of a low melting point metal such as aluminum or magnesium is interposed between the metal foil and the boron layer to provide high rigidity, high elasticity and high bonding strength between the metal foil and the boron layer.