Peculiarities of magnetotransport properties of Mo$_x$W$_{1-x}$Te$_2$ (x = 0; 0.7) single crystals

The magnetotransport properties of Mo$_{0.7}$W$_{0.3}$Te$_{2}$ and WTe$_{2}$ single crystals were studied at temperatures from 4.2 to 80 K and in magnetic fields up to 10 T. The concentrations and mobilities of electron and hole current carriers were estimated in the studied samples at a temperature of 4.2 K. It was found that the carrier mobility in the WTe$_{2}$ single crystal is an order of magnitude higher than the values obtained for Mo$_{0.7}$W$_{0.3}$Te$_{2}$, which is associated with its higher “electrical” purity. A minimum of the temperature dependence of the resistivity of WTe$_{2}$ was found in a magnetic field of 10 T at a temperature of 60 K, which can be explained by the transition from effectively high magnetic fields to weak ones. The absence of such a minimum for the Mo$_{0.7}$W$_{0.3}$Te$_{2}$ single crystal is due to the fact that the region of effectively high magnetic fields is not reached for it. The Hall resistivity of WTe$_{2}$ was shown to depend quadratically on the magnetic field at a temperature of 4.2 K, which is associated with the decompensation of electrons and holes, as well as with the scattering of charge carriers on the surface of the sample. Whereas for Mo$_{0.7}$W$_{0.3}$Te$_{2}$, along with the quadratic contribution, a linear contribution to the Hall resistivity was observed, the cause of which may be the presence of a large number of defects and impurities in the crystal, which leads to a decrease in the mean free path of carriers and, consequently, to a decrease in the contribution of electron-surface scattering.