Unusual metalinsulator transition in disordered ferromagnetic films

摘要

We present a theoretical interpretation of recent data on the conductance near and farther away from the metalinsulator transition in thin ferromagnetic Gd films of thickness b≈210 nm. For increasing sheet resistances a dimensional crossover takes place from d=2 to d=3 dimensions, since the large phase relaxation rate caused by scattering of quasiparticles off spin wave excitations renders the dephasing length Lφ?b at strong disorder. The conductivity data in the various regimes obey fractional power-law or logarithmic temperature dependence. One observes weak localization and interaction induced corrections at weaker disorder. At strong disorder, near the metalinsulator transition, the data show scaling and collapse onto two scaling curves for the metallic and insulating regimes. We interpret this unusual behavior as proof of two distinctly different correlation length exponents on both sides of the transition.