INHOMOGENEOUS MAGNESIUM HYDRIDE SYNTHESIZED BY LOW-TEMPERATURE ION-IMPLANTATION - WEAK-LOCALIZATION EFFECT

Metastable MgH(x) hydride was prepared by H ion implantation into Mg f ilms at 5 K. The resistivity and magnetoresistance temperature depende nce reveal weak localization effects due to atomic disorder. At low hy drogen concentrations, x less-than-or-equal-to 0.3, the conductivity v aries as sigma is similar to log(T), typical of two-dimensional weak l ocalization behaviour. The resistivity is also very sensitive to the s ample inhomogeneity, due to H diffusion, which can be modelled by intr oducing a temperature-dependent geometrical percolating factor G. At h igher H concentrations, 0.7 less-than-or-equal-to x less-than-or-equal -to 3, after annealing at 20 K, 50 K and 110 K, the samples also exhib it weak localization but with three-dimensional behaviour i.e. sigma i s similar to square-root T. Our analysis is consistent with the existe nce of an inhomogeneous system formed by a mixture of two phases with contrasted conduction properties, one of which is a well-behaved metal , while the other displays the localization properties. The results le ad us to identify the former phase to a non percolating superconductin g phase at low temperature.