Modelling in-plane magneto-transport in Cr2AlC

Abstract

The ternary MAX phase Cr2AlC exhibits a noticeable variation of in-plane Hall coefficient with temperature, T. In previous work, this was assumed to be due to temperature dependent electron and hole concentrations, an unlikely conjecture for a highly metallic-like conducting ceramics like Cr2AlC. Herein we show that a realistic analytic approximation of the Fermi surface as measured by Angle Resolved Photo-Emission Spectroscopy or as computed by Density Functional Theory allows us to recover the main features of the in-plane magneto-transport (temperature variations of Hall coefficient, resistivity and magnetoresistance). The temperature variation is explained by the combined contribution of electron and hole bands, taking into account the local curvature of the Fermi surface and an appropriate and physically sound temperature variation of the relaxation time in each band. The model also allows us to retrieve the apparent (and erroneous) carrier densities as extracted when using conventional methods. We suggest that our explanation could be generalized to other MAX phases, for which more “involved” explanations have been advanced so far.