Studies of Ga NMR in EuGa4

EuGa 4 orders antiferromagnetically at T N ≈ 16 K with a effective magnetic moment of about 7.86 µ B .In the paramagnetic phase, the magnetic susceptibility of EuGa 4 follows the Curie-Weiss law with a positive Curie-Weiss temperature θ P = +3 K.In order to microscopically investigate the magnetic property of EuGa 4 in the paramagnetic state, the 69&71 Ga NMR measurements of EuGa 4 have been carried out at temperatures between 60 and 300 K. From the Ga NMR spectra indicating anisotropic configurations, the isotropic part K iso and anisotropic part K aniso of Knight shift, and nuclear frequncy ν Q are obtained.The K iso and K aniso shift to negative side with decreasing temperature due to the RKKY interaction.These temperature dependences follow the Curie-Weiss law with θ P = +3 K, which is consistent with that of the magnetic susceptibility.From the K -χ plot, the values of the hyperfine fields H hf iso and H hf aniso are -6.491 and -0.363 kOe/µ B , respectively.The ratio H hf aniso / H hf iso is 5.6 %.The observed 69&71 Ga spectra in the paramagnetic phase are assigned to the Ga(II) site because the values of ν Q in the paramagnetic state is very close to those in the antiferromagnetic state.