At the heart of XtremeSense® TMR technology is a thin-film magneto-resistive device, the so-called Magnetic Tunnel Junction (MTJ). In its simplest form the MTJ consists of two electrically-conducting magnetic layers on either side of a thin (nanometer-scale) but highly robust insulating layer. One magnetic layer has a fixed magnetic moment direction while the other can change freely to follow the direction of the local magnetic field.
Despite how thin the insulating layer is, it should prevent any current flow between the two magnetic layers, according to classical physics. However, in this nano-world, quantum physics allows electrons to “tunnel” across the atoms of the thin insulating material, with a resistance that depends sensitively on the relative orientation of the two magnetic layers. Therefore, as the Free layer magnetization follows the direction and intensity of the ambient magnetic field, its magnetic orientation is modified with respect to the Reference layer. This change in relative magnetic orientation will significantly change the probability of quantum tunneling between the two layers and therefore the electron flow through the device.