Direct measurement of anisotropic conductivity in a nanolaminated (Mn0.5Cr0.5)2GaC thin film.

The direct and parameter-free measurement of anisotropic electrical resistivity of a magnetic Mn+1AXn (MAX) phase film is presented. A multitip scanning tunneling microscope is used to carry out 4-probe transport measurements with variable probe spacing s. The observation of the crossover from the 3D regime for small s to the 2D regime for large s enables the determination of both in-plane and perpendicular-to-plane resistivities ρab and ρc. A (Cr0.5Mn0.5)2GaC MAX phase film shows a large anisotropy ratio ρ c / ρ ab = 525 ± 49. This is a consequence of the complex bonding scheme of MAX phases with covalent M–X and metallic M–M bonds in the MX planes and predominately covalent, but weaker bonds between the MX and A planes. [ABSTRACT FROM AUTHOR]