Patent ID: 7138798

Claim:
An azimuth meter comprising a plane coil having two pairs of opposed sides which are at least partially parallel to each other, the pairs being perpendicular to each other; and two pairs, per pair of the opposed sides of the plane coil, of spin-valve giant magneto-resistive elements positioned on the same side of a plane of the plane coil and on a plane parallel and close to the plane of the plane coil, wherein: each of the spin-valve giant magneto-resistive elements is a multi-layered thin film formed by sandwiching a nonmagnetic layer between a pinned layer made of a ferromagnetic substance magnetically coupled with an antiferromagnetic layer made of an antiferromagnetic substance and a free layer made of a ferromagnetic substance, the multi-layered thin film having a shape whose widthwise dimension is sufficiently small relative to a longitudinal dimension thereof, a longitudinal direction of one spin-valve giant magneto-resistive element of each pair of the spin-valve giant magneto-resistive element pairs and that of the other spin-valve giant magneto-resistive element of the pair orthogonally cross each other, the pinned layer of the one spin-valve giant magneto-resistive element is magnetized in its longitudinal direction and the pinned layer of the other spin-valve giant magneto-resistive element is magnetized in the same direction as the pinned layer of the one spin-valve giant magneto-resistive element; the longitudinal directions of the two spin-valve giant magneto-resistive elements constituting each pair of the spin-valve giant magneto-resistive element pairs cross only a respective side or only the same side of the pair of the opposed sides of the plane coil at substantially 45 degrees; and the two spin-valve giant magneto-resistive elements of each pair of the spin-valve giant magneto-resistive element pairs are connected to each other at one end of each of the two spin-valve giant magneto-resistive elements, and a voltage for measurement is applied between the other ends of the two spin-valve giant magneto-resistive elements to enable a midpoint potential to be taken out of the one end.