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

Abstract

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 Zn_65.2Mg_27.9Ho_6.9 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.

Acknowledgements

The authors thank Drs H. Takakura, K. Shibata, H. Kadowaki, T. Onimaru and J. W. Lynn for stimulating discussions. This work was partly supported by a Grant-in-Aid for Encouragement of Young Scientists (B) (No. 16760537) and by a Grant-in-Aid for Creative Scientific Research (No. 16GS0417) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.