Hall effect in crystalline Ni-Fe-Cr alloys showing resistivity minima

Abstract

The temperature dependence of Hall resistivity $({\ensuremath{\rho}}_{H})$ is presented for magnetic inductions up to 1.3 T and temperatures down to 1.4 K. The samples are ferromagnetic Ni-rich $\ensuremath{\gamma}\ensuremath{-}{\mathrm{Ni}}_{75}{\mathrm{Fe}}_{13}{\mathrm{Cr}}_{12}$ (sample 1), ${\mathrm{Ni}}_{70}{\mathrm{Fe}}_{12}{\mathrm{Cr}}_{18}$ (sample 2), and ${\mathrm{Ni}}_{73.5}{\mathrm{Fe}}_{8}{\mathrm{Cr}}_{18.5}$ (sample 3) alloys. The values of the ordinary ${(R}_{0})$ and the extraordinary ${(R}_{s})$ Hall coefficients are found to be positive in samples 2 and 3 whereas they are negative in sample 1. Electrical-resistivity $[\ensuremath{\rho}(T)]$ studies in these alloys have shown resistivity minima (at ${T}_{\mathrm{min}}$) that are described by electron-electron interaction effects. ${R}_{0}$ is found to be nearly temperature independent in all the alloys. On the other hand, ${R}_{s}(T)$ has shown minima, very similar to those of $\ensuremath{\rho}(T)$ around ${T}_{\mathrm{min}}.$ The temperature dependence of the positive extraordinary Hall coefficient in samples 1 and 3 is consistent with the minima observed in $\ensuremath{\rho}(T),$ whereas the negative extraordinary Hall coefficient in sample 1 behaves exactly opposite to what is expected theoretically, i.e., instead of getting more negative, the coefficient becomes more positive on both sides of ${T}_{\mathrm{min}}.$ This is found to be rather puzzling and cannot be explained in terms of the existing theories. However, the positive ${R}_{s}(T)$ is interpreted indirectly (through their electrical resistivity) by electron-electron interaction effects.