A magnetoresistive stack includes a reference layer including a magnetic layer, an antiferromagnetic layer in exchange coupling with the magnetic layer, a magnetic layer substantially of the same magnetisation as the magnetic layer, a spacer layer between the magnetic layers with a thickness for enabling an antiferromagnetic coupling between the magnetic layers of a first coupling intensity, a free layer having a coercivity of less than 10 microTesla, the free layer including a magnetic layer, an antiferromagnetic layer in exchange coupling with the magnetic layer, a magnetic layer substantially of the same magnetisation as the magnetic layer, a spacer layer between the magnetic layers with a thickness for enabling an antiferromagnetic coupling between the magnetic layers of a second coupling intensity lower than the first coupling intensity, a third spacer layer separating the reference and free layers.