Аннотация:As the composition of granular aluminum is varied the fractional negative magnetoresistance goes through a maximum at the metal-insulator transition. We have measured a decrease in resistance as high as 98.5%, apparently limited only by the lowest temperature and the highest field in the experiment, as well as by the closeness of the specimen to the transition. The change with field of the temperature dependence of the resistivity demonstrates that a magnetic field shifts an insulating specimen closer to the metal-insulator transition. The dependence of the resistance on field can be used to determine the localization length of insulating specimens.
