PURPOSE: To obtain the high magnetic susceptibility by applying a unidirectional switched connection magnetic field to the difficult axis direction of a ferromagnetic thin film.

CONSTITUTION: A main magnetic pole 21, a connection magnetic film 23 and a magnetic substrate 24 constitute one magnetic circuit. In this case, a signal magnetic field from a magnetic recording medium 28 propagates through this magnetic circuit, and is interlinked to a thin film coil 25. In this case, induction electromotive force is generated in the thin film coil 25, any by reproducing this voltage variation, an information signal from the magnetic recording medium 28 can be detected. In such a state, with respect to the main magnetic pole 21, a switched connection magnetic field HUA is applied in its difficult axis direction. In such a way, the magnetic susceptibility of the main magnetic pole 21 becomes high, and the reproducing efficiency of the signal magnetic field becomes high.