Giant Magnetoresistance (GMR)
A quantum spintronic phenomenon where electrical resistance drops dramatically when adjacent ferromagnetic layers align magnetically parallel in an external field.
Governing formula
GMR = (R_AP - R_P) / R_P × 100%
SI unit
% (Resistance Change Ratio)
In depth
Discovered by Albert Fert and Peter Grünberg in 1988 (Nobel Prize 2007). In thin-film ferromagnetic/non-magnetic multilayers, spin-dependent electron scattering is minimized when magnetization vectors align parallel.
Examples in the real world
Ultra-sensitive GMR read heads in computer hard disk drives increasing data storage density by orders of magnitude.