Characterization of the natural barriers of intergranular tunnel junctions: Cr2O3 surface layers on CrO2 nanoparticles
Cold-pressed powder compacts of CrO2 show large negative magnetoresistance (MR) due to intergranular tunneling. Powder compacts made from needle-shaped nanoparticles exhibit MR of about 28% at 5 K. Temperature dependence of the resistivity indicates that the Coulomb blockade intergranular tunneling is responsible for the conductance at low temperature. In this letter we report direct observation and characterization of the microstructure of the intergranular tunnel barriers, using transmission electron microscopy, x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). A very thin ...
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