Giant magnetoresistance in PtMn alloys

The giant magnetoresistance in PtMn alloys was studied. It was shown that the onset of chemical and magnetic order in PtMn was accompanied by a large increase in the resistivity, ρ, contrary to that observed in nonmagnetic or ferromagnetic disorder-order transitions. It was observed that the characterstics of the resistance change with anneal time in two regimes, with only the second regime involving a disorder/order transition. The change of ρ with time was used to calculate the activation energy for the L1 0 transformation in PtMn.