1. A magnetic device comprising a magnetoresistive tunnel junction, itself comprising: a reference magnetic layer having magnetization in a direction that is fixed; a storage magnetic layer having magnetization in a direction that is variable; and an intermediate layer acting as a tunnel barrier that is essentially semiconductor or electrically insulating and that separates the reference magnetic layer from the storage magnetic layer; the device being characterized in that the potential profile of the intermediate layer is asymmetrical across the thickness of said layer so as to produce a current response that is asymmetrical as a function of the applied voltage.