PURPOSE: To execute magnetic recording of ≥2 kinds of different track widths by one magnetic core by forming the one magnetic core of core members consisting of ≥2 kinds of materials varying in magnetic permeability.

CONSTITUTION: The core members 1, 3 and the core members 2, 4 are disposed to face each other on both sides of a gap 5. The magnetic field Hg of the gap 5 is the value determined by the track width, the magnetic permeability and writing current. The writing only at the track width (a) is executed if the Hg at the track width (a) is designated as Hg1 and the Hg at the track width (c) as Hg2 and if the writing is executed by such writing current as to attain Hg1>K, Hg2<K. The writing at the track width (b) (including the track width (c)) is possible if the writing is executed by such writing current as to attain Hg1>K, Hg2>K.