Magnetic field detector and manufacturing method thereof

A magnetic field detector comprising:

• a magnet;
• a detecting magnetic resistance element detecting an external magnetic field and having a layer structure including a ferromagnetic layer, the resistance of the detecting magnetic resistance element being changed by a change in magnetizing direction of the ferromagnetic layer;
• and
• first and second reference magnetic resistance elements having substantially the same layer structure as the detecting magnetic resistance element, wherein
• the detecting magnetic resistance element is substantially coplanar with the first and second reference magnetic resistance elements and is centrally disposed between the first and second reference magnetic resistance elements,
• the magnet impresses a magnetic field having an intensity not less than a saturation magnetic field of the first and second reference magnetic resistance elements in directions in which the ferromagnetic layers of the first and second reference magnetic resistance elements sense a change in magnetic field, and
• the magnet impresses a magnetic field in a direction in which the ferromagnetic layer of the detecting magnetic resistance element does not sense a change in magnetic field.