Anomalous Hall effect related to the magnetization in pure decagonal Al-Mn phases

Abstract

An anomalous Hall effect is measured in pure decagonal ${\mathrm{Al}}_{80}$${\mathrm{Mn}}_{20}$ and ${\mathrm{Al}}_{78}$${\mathrm{Mn}}_{22}$. We show that the Hall resistivity ${\mathrm{\ensuremath{\rho}}}_{\mathit{H}}$ is linear with the magnetization M measured for the same fields and temperatures: ${\mathrm{\ensuremath{\rho}}}_{\mathit{H}}$(H,T)=${\mathit{R}}_{0}$H+4\ensuremath{\pi}${\mathit{R}}_{\mathit{S}}$M(H,T). The very dominant term ${\mathit{R}}_{\mathit{S}}$M of ${\mathrm{\ensuremath{\rho}}}_{\mathit{H}}$ reveals a strong spin-orbit scattering, which is observed in Al-Mn quasicrystals. ${\mathit{R}}_{\mathit{S}}$ is found to be temperature independent in the range 6.5--110 K. From our susceptibility, specific-heat, and magnetoresistance data, we deduce that M results from a very low fraction of magnetic moments, which increase drastically with the nominal Mn concentration and that are correlated by Ruderman-Kittel-Kasuya-Yosida interactions. In this respect, the Al-Mn decagonal phase behaves very similarly to previously measured Al-Mn icosahedral and amorphous phases.