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Hellman, F., M. Q. Tran, A. E. Gebala, E. M. Wilcox, and R. C. Dynes, 1996: Metal-Insulator Transition and Giant Negative Magnetoresistance in Amorphous Magnetic Rare Earth Silicon Alloys. Phys. Rev. Lett., 77, 4652-4655. AbstractLarge negative magnetoresistance and anomalous magnetic properties are found in amorphous Si
doped with magnetic rare earth ions near the metal-insulator transition. The resistivity below 50 K rises orders of magnitude above that of comparable composition nonmagnetic alloys and is strongly reduced by a magnetic field. Magnetization measurements show noninteracting moments at high temperature which develop antiferromagnetic interactions below 50 K. We suggest that these results are due to formation below 50 K of a dense concentration of magnetic polarons which localize conduction electrons. |
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