Sensor for detecting a period magnetic field

A sensor for detecting a periodic magnetic field comprising a measuring assembly integrating at least one magnetoresistive element the electrical resistance of which varies as a function of the amplitude of the component of said periodic magnetic field in a direction X, said magnetoresistive element comprising a stack of two conductive magnetic layers, respectively reference and sensitive, between which a separation layer is disposed so that the electrical resistance of said stack is dependent on the relative orientation of the magnetization of the reference and sensitive layers, said sensor further comprising an electronic circuit arranged so as to use the variations in said electrical resistance in order to deliver a signal representing the magnetic field to be detected, the reference layer having magnetic anisotropy in the direction X and the sensitive layer having a direction Y perpendicular to the direction X, said sensor including a permanent polarization magnet having a surface extending in a plane of directions X and Y and having a symmetry plane of directions X and Z, the direction Z being perpendicular to the directions X and Y and being the direction along which the magnetic field of said magnet mainly extends, the measuring assembly being disposed with respect to the symmetry plane of the polarization magnet so that the layers of the magnetoresistive element are disposed in a plane parallel to the surface while being offset from said plane in the direction Y by a distance (Δy) that is arranged so that the magnetic field of the polarization magnet orients the magnetization of the sensitive layer in the direction Y while allowing variations in the orientation of said magnetization according to the component of the direction X of the magnetic field to be detected, said variations in magnetization causing a linear variation in the electrical resistance of the magnetoresistive element over a magnetic field range to be detected.