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Giant magnetoresistance connects the relative magnetizations of adjacent magnetic layers to their electrical transport. In a suitable magnetic-metal/nonmagnetic-metal stack, aligning the layers can leave one spin channel with an easy conducting path through both magnetic layers; opposite alignments make each channel encounter a more resistive layer. Albert Fert's account traces the spin-dependent-conduction idea to Nevill Mott and distinguishes the later device geometries.^[ref]

The beauty is that a magnetic arrangement becomes an electrical readout. Preparing reproducible layers, establishing their magnetizations, and measuring electrical resistance are separate parts of that inference. The Fe-Cr giant magnetoresistance experiments show how those parts were joined; the two-current resistor model isolates a simple transport mechanism under stated assumptions.

Nevill Mott investigated electronic conduction in disordered solids, including glasses and amorphous semiconductors. When states are localized, a carrier can move by thermally assisted hopping rather than ordinary propagation through an extended band. The useful hopping distance balances weak overlap at long range against the availability of energetically accessible states. This connects a temperature-dependent conductivity with both the spatial localization and energy distribution of electronic states.^[ref]

A physicist.^[ref]