Sb NQR Studies of Ferromagnetism in YbxFe4Sb12 with x≈0.89

121,123 Sb nuclear quadrupole resonance (NQR) measurements have been performed for a polycrystalline sample of Yb x Fe 4 Sb 12 with x ≈0.89. Five well-separated NQR lines were observed above 18 K, which are explained by the quadrupole frequencies 121 ν Q =38.96 MHz, 123 ν Q =23.64 MHz, and the asymmetry parameter η=0.37. The NQR lines broaden after the divergence of the Sb-NQR spin lattice relaxation rate, 1/ T 1 , around 18 K, which corresponds to the internal magnetic field of ∼ 2700 G at the Sb site. Together with magnetization measurements, the present results indicate that the electronic state in Yb x Fe 4 Sb 12 ( x ≈0.89) changes from a paramagnetic to a ferromagnetic state at T C ≈18 K.