Magnetic detection element utilizing magneto-impedance effect, production method of the element, and portable equipment using the element
A magnetic detection element suitable for detecting a strength of an external magnetic field, has a magnetic thin film formed on a single non-magnetic substrate, a circuit that applies a high-frequency current to the magnetic thin film, and a spiral-type planar coil that is stacked on the magnetic thin film with an insulating layer, in between. The magnetic thin film is formed in a longitudinal shape, and magnetic anisotropy is provided such that the direction of easy magnetization is orthogonal to the longitudinal direction of the longitudinal shape.
1. A magnetic detection element for detecting a strength of an external magnetic field, comprising:
a magnetic thin film formed on a single non-magnetic substrate;
a circuit that applies a high-frequency current to the magnetic thin film; and
a spiral-type planar coil that is stacked on the magnetic thin film through an insulating layer between the coil and the film,
wherein the magnetic thin film is arranged between a center and an end of the planar coil so that respective lines of the planar coil cross the magnetic thin film, and a line pitch of the planar coil crossing the magnetic thin film is larger than a line pitch of another portion of the planar coil, and
wherein the magnetic thin film is formed in a longitudinal shape and has magnetic anisotropy such that the direction of easy magnetization is orthogonal to a longitudinal direction of the longitudinal shape.
2. The element according to claim 1 , further comprising:
a circuit that supplies a current to the planar coil so as to apply a bias magnetic field to the magnetic thin film; and
a circuit that detects a change in impedance of the magnetic thin film.
3. The element according to claim 2 , wherein a line pitch S of the planar coil in a portion crossing the magnetic thin film is 8 μm ≦S≦50 μm.
4. The element according to claim 2 , wherein a line pitch S of the planar coil in a portion crossing the magnetic thin film is 8 μm≦S≦25 μm.
5. The element according to claim 1 , wherein the planar coil comprises two coils that are arranged so that each coil has a center located at a separate end of the magnetic thin film, and wherein the coils are mutually connected.
6. The element according to claim 1 , wherein a leading electrode is formed so as to overlie the planar coil with another insulating layer between the coil and the electrode.
7. The element according to claim 1 , further comprising:
a circuit that detects a change of an induced voltage generated in the planar coil.
8. Portable equipment comprising an azimuth sensor formed by arranging magnetic detection elements according to claim 1 so as to be mutually orthogonal.