Magnetic excitations in the crystalline and quasicrystalline Zn–Mg–Ho phases

A comparative study has been carried out on magnetic excitations in the primitive- (p-) and face-centred- (f-) icosahedral quasicrystalline phases, as well as crystalline phase, in the Zn–Mg–Ho system. The magnetic excitation spectrum in both the quasicrystalline phases has only a broad quasielastic peak centred at the elastic position; the signal for the positive energy-transfer (ℏω) side is found to be almost temperature independent in a wide temperature range 1.5 <T <200K. The magnetic excitation spectrum in the crystalline Zn65.2Mg27.9Ho6.9 phase is quite similar to that of the quasicrystalline phases at high temperatures; however, well-defined inelastic peaks due to crystalline-electric-field (CEF) splitting levels appear as the temperature is decreased. The appearance of the sharp CEF peaks confirms well-defined site symmetry around the rare-earth sites in the hexagonal phase, whereas the temperature-independent quasielastic signal suggests anomalous spin fluctuations in the quasicrystalline phases.