Interplay between hybridization gaps and antiferromagnetic gap in the hole-doped Kondo semiconductor Ce(Os1-yRey)2Al10

Abstract

The Kondo semiconductor CeOs₂Al₁₀ undergoes an antiferromagnetic (AFM) order at an unexpectedly high temperature 28.5 K. We have performed break junction tunneling measurements for the hole-doped system Ce(Os_1-yRe_y)₂Al₁₀ (y ≤ 0.1). The tunneling spectrum dI/dV for y = 0 displays successive openings of a hybridization gap V₁, an AFM gap V_AF and another hybridization gap V₂ in the density of states (DOS). On cooling from 36 K to T_N, both the gap value V₁ and the DOS at the Fermi level, E_F, decrease by 8% of the values at 36 K. This fact indicates that the development of short-range magnetic correlations reduces the c-f hybridization gap. For y = 0.02, a peak appears in dI/dV at V = 0 concurrently with the disappearance of V₂. With increasing y further, the in-gap states develop at E_F, in good agreement with the increase in the Sommerfeld coefficient of the heat capacity. Thereby, T_N, V₁ and V_AF decrease and disappear at y = 0.05. These facts provide compelling evidence that the presence of V₁ is necessary for the AFM order in CeOs₂Al₁₀.