Magnetic ground states and excitation in hexagonal metal Ce₂Zn₁₇

In contrast to the long-range ordering of dipolar magnetic moments, scenarios such as multipolar ordering and frustration-induced liquid state are less established experimentally. Here we report experimental results in hexagonal metal Ce₂Zn₁₇ where these scenarios are likely relevant. Ce₂Zn₁₇ demonstrated a putative antiferromagnetic transition at T_N = 1.59K, defined by a sharp peak in heat capacity and drop of magnetic susceptibility, with an entropy change of ~Rln2. However, no magnetic Bragg peaks were observed below T_N from diffraction. On the other hand, we documented a coherent magnon mode around Q = (0.5 0.5 0) in the inelastic scattering spectrum, with the band top of ~0.5meV and likely a gap size of 0.1meV. We further present the temperature-, field-, and polarization-dependence of the excitation spectrum.