Spin dynamics in the electron-doped Kondo insulatorYb1−xZrxB12(x=0.2)

Abstract

Electron doping of the Kondo insulator ${\text{YbB}}_{12}$ has been achieved by substitution of tetravalent Zr in the newly synthesized ${\text{Yb}}_{0.8}{\text{Zr}}_{0.2}{\text{B}}_{12}$ solid solution. Neutron-scattering measurements of the spin dynamics are reported, together with electrical resistivity and ac magnetic-susceptibility data. Zr doping transforms the spin-gap spectral response into a pseudogap shape and makes its temperature evolution much smoother than in the ${\text{Yb}}_{1\ensuremath{-}x}{\text{Lu}}_{x}{\text{B}}_{12}$ family studied previously. The results obtained are discussed in connection with the local bound-state picture for the Kondo insulator.