Magnetic head with glass used to bond together two core halves having a coefficient of thermal expansion less than that of the ferromagnetic oxide used to make the core halves

A magnetic head, comprising:

• a pair of C-shaped magnetic core halves made of a ferromagnetic oxide, at least one of which has a groove for receiving a coil;
• a gap filler material which fills a magnetic gap which exists when the core halves are bonded together;
• track width controlling grooves formed on opposite sides of the magnetic gap;
• and
• glass bonding the core halves together, the glass filling the track width controlling grooves to bond the core halves together;
• a coefficient of thermal expansion of the glass, as measured between 100 and 350 degrees Celsius, is 20.times.10.sup.-7 to 35.times.10.sup.-7 per degree Celsius less than that of the ferromagnetic oxide;
• the gap has a length of 0.35 .mu.m or less,
• the head has a track width of 25 .mu.m or less,
• the bonding of the core halves is conducted with the viscosity of the glass between 4.4 and 4.7 Pa*s, and
• the pressure applied to the gap between the core halves in the bonding process is 50 kg*f/cm.sup.2 or less.