A magnetic head comprises a substrate, a soft magnetic thin film, whose magnetic permeability varies according to the intensity of an external magnetic field applied thereto, formed over the surface of the substrate, means for supplying a high-frequency current to the soft magnetic thin film, and means for applying a bias magnetic field to the soft magnetic thin film. The magnetic permeability of the soft magnetic thin film varies according to the variation of the intensity of the external magnetic field and hence the potential difference between the opposite ends of the soft magnetic thin film with respect to the direction of flow of the high-frequency current varies accordingly. The variation of the potential difference is detected for magnetic signal reading. The soft magnetic thin film is formed of a material having a large magnetic permeability, such as amorphous CO.sub.75 Ta.sub.11 Zr.sub.14.