Ac-suseptibility measurements were performed in the metallic helimagnet Gd_{1-x}Y_{x} alloy. A remarkable increase of the imaginary part of the ac-suseptibility was observed in the temperature range of the helimagnetic phase. Moreover, a strong nonlinearity of the magnetization was observed at paramagnetic-helimagnetic transition temperature T_{N}. On the other hand, These anomalous behavior were not observed in similar rare-earth helimagnets Ho and Ho_{1-x}Y_{x}. It strongly suggests that the weak magnetic anisotropy of the Gd-moments is responsible for the anomalous slow dynamics in the helimagnetic phase and for the strong nonlinearity of the magnetization at T_{N}. The slow dynamics may result from a chiral-domain motion, or a long-time variation of the period of the helimagnetic structure.
@article{arxiv.1106.3730,
title = {Anomalous slow dynamics in the metallic helimagnet Gd_{1-x}Y_{x}},
author = {Teruo Yamazaki and Yohikazu Tabata and Takeshi Waki and Hiroyuki Nakamura},
journal= {arXiv preprint arXiv:1106.3730},
year = {2014}
}