The Metal-Insulator Transition in Metal Transition Granular Films

N.E. MASSA; J.C. DENARDIN,; L. SOCOLOSKY; M. KNOBEL; X.X. ZHANG

Baltimore, Maryland, U.S.A.

Congreso; American Physcial Society March Meeting; 2006

American Physical Society

We study with infrared re°ectivity the concentration and temperature de- pendence of the regime change from metallic to insulating in granular ¯lms made of transition metals embedded in SO2. The TMx(SO2)1¡x2. The TMx(SO2)1¡x (TM=Fe, Ni, Co), (0.25·x·0.85) systems yield spectra typical of con- ducting oxides where hopping carriers undergo electron-phonon interac- tions with localization enhanced by nanoparticles and substrate rough- ness. The distinct Drude component, extending beyond 1.3 eV in the metallic state, undergoes a dramatic change in intensity due to the pro- gressive reduction of carriers critical paths as the transition temperature is reached in the glassy matrix. At the intermediate conducting state for x» 0.55, about the percolation threshold, a well de¯ned re°ectivity edge and band, considered ¯ngerprint for small polarons, emerges in addition to the vibrational bands. A very good agreement is found between the measured optical conductivity and current small polaron models. This, in addition to underlying the importance of polarization e®ects, provides grounds toward a quantitative microscopic description of transport prop- erties. It also adds toward an understanding of a non-magnetic factor in the magnetoresistance and extraordinary Hall coe±cient enhancements. and band, considered ¯ngerprint for small polarons, emerges in addition to the vibrational bands. A very good agreement is found between the measured optical conductivity and current small polaron models. This, in addition to underlying the importance of polarization e®ects, provides grounds toward a quantitative microscopic description of transport prop- erties. It also adds toward an understanding of a non-magnetic factor in the magnetoresistance and extraordinary Hall coe±cient enhancements. ducting oxides where hopping carriers undergo electron-phonon interac- tions with localization enhanced by nanoparticles and substrate rough- ness. The distinct Drude component, extending beyond 1.3 eV in the metallic state, undergoes a dramatic change in intensity due to the pro- gressive reduction of carriers critical paths as the transition temperature is reached in the glassy matrix. At the intermediate conducting state for x» 0.55, about the percolation threshold, a well de¯ned re°ectivity edge and band, considered ¯ngerprint for small polarons, emerges in addition to the vibrational bands. A very good agreement is found between the measured optical conductivity and current small polaron models. This, in addition to underlying the importance of polarization e®ects, provides grounds toward a quantitative microscopic description of transport prop- erties. It also adds toward an understanding of a non-magnetic factor in the magnetoresistance and extraordinary Hall coe±cient enhancements. and band, considered ¯ngerprint for small polarons, emerges in addition to the vibrational bands. A very good agreement is found between the measured optical conductivity and current small polaron models. This, in addition to underlying the importance of polarization e®ects, provides grounds toward a quantitative microscopic description of transport prop- erties. It also adds toward an understanding of a non-magnetic factor in the magnetoresistance and extraordinary Hall coe±cient enhancements. ·x·0.85) systems yield spectra typical of con- ducting oxides where hopping carriers undergo electron-phonon interac- tions with localization enhanced by nanoparticles and substrate rough- ness. The distinct Drude component, extending beyond 1.3 eV in the metallic state, undergoes a dramatic change in intensity due to the pro- gressive reduction of carriers critical paths as the transition temperature is reached in the glassy matrix. At the intermediate conducting state for x» 0.55, about the percolation threshold, a well de¯ned re°ectivity edge and band, considered ¯ngerprint for small polarons, emerges in addition to the vibrational bands. A very good agreement is found between the measured optical conductivity and current small polaron models. This, in addition to underlying the importance of polarization e®ects, provides grounds toward a quantitative microscopic description of transport prop- erties. It also adds toward an understanding of a non-magnetic factor in the magnetoresistance and extraordinary Hall coe±cient enhancements. and band, considered ¯ngerprint for small polarons, emerges in addition to the vibrational bands. A very good agreement is found between the measured optical conductivity and current small polaron models. This, in addition to underlying the importance of polarization e®ects, provides grounds toward a quantitative microscopic description of transport prop- erties. It also adds toward an understanding of a non-magnetic factor in the magnetoresistance and extraordinary Hall coe±cient enhancements. » 0.55, about the percolation threshold, a well de¯ned re°ectivity edge and band, considered ¯ngerprint for small polarons, emerges in addition to the vibrational bands. A very good agreement is found between the measured optical conductivity and current small polaron models. This, in addition to underlying the importance of polarization e®ects, provides grounds toward a quantitative microscopic description of transport prop- erties. It also adds toward an understanding of a non-magnetic factor in the magnetoresistance and extraordinary Hall coe±cient enhancements.