Giant magnetoresistance: history, development and beyond

With the discovery of giant magnetoresistance (GMR), research effort has been made to exploiting the influence of spins on the mobility of electrons in ferromagnetic materials and/or artificial structures, which has lead to the idea of spintronics. A brief introduction is given to GMR effects from scientific background to experimental observations and theoretical models. In addition, the mechanisms of various magnetoresistance beyond the GMR are reviewed, for instance, tunnelling magnetoresistance, colossal magnetoresistance, and magnetoresistance in ferromagnetic semiconductors, nanowires, organic spintronics and non-magnetic systems.