Unusual metal–insulator transition in disordered ferromagnetic films

• Published in: Physica. B, Condensed matter Condensed matter, 2012-10, Vol.407 (20), p.4023-4026
• Main Authors: Muttalib, K.A., Wölfle, P., Misra, R., Hebard, A.F.
• Format: Article
• Language: English
• Subjects: Collapse; Condensed matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crossovers; Disordered systems; Disorders; Electron states; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Ferromagnetic films; Localization effects (anderson or weak localization); Metal-insulator transition; Metal-insulator transitions and other electronic transitions; Physics; Position (location); Surface and interface electron states; Temperature dependence
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2011.12.131

We 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≈2–10nm. 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 metal–insulator 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.