How does giant magnetoresistance work?
Imagine a sandwich of two magnetic layers separated by a non-magnetic spacer, like chromium. When the magnetic layers are aligned in the same direction, electrons with spin parallel to that direction pass through easily, giving low resistance. But if the layers are antiparallel—pointing opposite ways—electrons scatter more, and resistance jumps dramatically. This change can be over 50% at room temperature, which is why we call it 'giant.' The effect arises from spin-dependent scattering, a concept from spintronics. A good measurement is worth a thousand theories: we confirmed this by carefully measuring resistance as we varied the magnetic field. It’s a simple system that reveals a profound effect, and it’s now the basis for read heads in virtually every hard drive.
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