Unusual metal-insulator transition in disordered ferromagnetic films

(W)e present a theoretical interpretation of recent data on the conductance near and farther away from the metal-insulator transition in thin ferromagnetic Gd films of thickness b approximate to 2-10 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 L-phi less than or similar to 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 metal-insulator transition, the data show scaling and collapse on to 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. (c) 2012 Elsevier B.V. All rights reserved.