Non-magnetic element substitution effect in Kondo insulator YbB12 and exotic surface effect in this alloy system

摘要

Kondo temperature T K’s for Kondo insulator alloys Yb1- x R x B12 (R = Y, Lu, Sc and Zr) show drastic variation as every x increase. It is found that YbB12 in a virtual gap-less state would have a peak at about 25 K in magnetic susceptibility χ( T ) from analysis of χ( T ) of all these alloys. Up-turns shown in χ( T ) below 20 K grow as development of an energy gap Δ E . Those behaviors may be related to the second-gap development within the in-gap state showing metallic behaviors.