The magnetic properties of amorphous Al x Fe100−x alloys investigated by the atomic structure, magnetoresistance and anomalous Hall effect

We report on experimental results of the specific resistivity $\rho$, Hall resistivity ${\rho }_H$ and magnetoresistance MR of rapidly quenched Al_xFe_100−x binary amorphous alloys. Atomic structure investigation done by transmission electron microscopy at room temperature verifies that samples are in the pure amorphous state with a high coordination number $8<N_c<12$. Systematic changes in the resistivity, magnetoresistance and Hall effect were observed with the varying Fe content. At room temperature, samples with Fe content $⩾40\%$ show negative magnetoresistance, are p-type and show the presence of anomalous Hall effect, while samples with Fe content $⩽25\%$ show positive magnetoresistance, are n-type and show no anomalous Hall effect contribution. Our experimental results are discussed in the concept of electronic stabilization Hume-Rothery amorphous alloys triggered by the hybridization effect of the Fe-d and the Al-$s,p$ electrons. Previous literature results have predicted that when the Fe-d states are full, no ferromagnetic properties should be observed in the Al_xFe_100−x alloys, and this is for concentrations $x⩾75$, which is in agreement with our results, because the appearance of an anomalous contribution in the Hall effect would be a direct evidence of ferromagnetic order in the Al_xFe_100−x amorphous alloys.