Abstract
Abstract
We present here a new Tunnel Magneto Resistance (TMR) sensor used for measuring magnetic field in position, speed and direction of rotation applications. The physical principle behind Magnetic Tunnel Junctions (MTJ) is Spintronics, a novel branch of physics using not only the electrical charge of the electron, but also its quantum spin value. A MTJ is basically composed of two ferromagnetic layers separated by a very thin isolating layer. One of the magnetic layer (called the reference or hard layer) is pinned, i.e. does not move with the external magnetic field to be measured, and the other one (called the detection or soft layer) is not. The resistance of the structure depends on the orientation of the magnetization of both layers. The sensor we present here is designed so that the resistance of the MTJ is linear and reversible with the external magnetic field. Its sensitivity is independent of temperature and can be adapted by design to different magnetic field ranges, from low (< 1 Oe) to high fields (> 100 Oe). Its low power consumption, its good signal to noise ratio as well as its potentially high temperature working range, open great industrial opportunities.