Influence of an electron doping on spin dynamics of YbB_(12)

摘要

Electron doping of the Rondo-insulator YbB_(12) has been achieved by substitution tetravalent Zr for Yb in the newly synthesized Yb_(0.8)Zr_(0.2)B_(12) solid solution and substitution carbon for B in boron cluster network with concentration order of 1% (Yb(B_(0.99)C_(0.01))_(12). Neutron scattering measurements of the dynamical magnetic response are reported and analyzed. Zr doping transforms the spin-gap spectral response into a pseudogap shape and makes its temperature evolution much smoother than in the Yb_(1-x)Lu_xB_(12) family studied previously. Carbon doping influences on the energy range of ground state excitation spectrum but does not suppress the magnetic gap. The results obtained are discussed in connection with the contribution of different interactions into the formation of the ground state for the Kondo-insulator.