Some Metal-Insulator Transitions in Various Materials

Some Metal-Insulator Transitions in Various Materials 

In some of the metal-insulator transitions discussed here the use of classical percolation theory has been used to describe the results. This will be valid if the carrier cannot tunnel through the potential barriers produced by the random internal field. This may be so for very heavy particles, such as dielectric or spin polarons. A review of percolation theory is given by Kirkpatrick (1973). One expects a conductivity behaving like 

This material, which has the ideal cubic perovskite structure, has been extensively investigated from both theoretical and experimental points of view (see Dougier 

Interaction either with phonons or spin waves might be responsible for the condition Lj a near the transition. At lower temperatures o in the metallic range should drop continuously to zero at the transition further observations are desirable to see if this is so. 

Section 6, but a mathematical treatment has not, as far as we know, been given. However the results shown in Fig. 7.5 make it very probable that it is so, if weak localization is present, though it appears unlikely without. 

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