Origin and dynamics of umbrella states in rare-earth iron garnets

Rare-earth iron garnets R3Fe5O12 are fascinating insulators with very diverse magnetic phases. Their strong potential in spintronic devices has encouraged a renewal of interest in the study of their low temperature spin structures and spin wave dynamics. A striking feature of rare-earth garnets with R-ions exhibiting strong crystal-field effects like Tb-, Dy-, Ho-, Er-, Tm-and Yb-ions is the observation of low-temperature non-collinear magnetic structures featuring umbrella-likearrangements of the rare -earth magnetic moments. In this study, we demonstrate that such umbrella magnetic states are naturally emerging from the crystal-field anisotropies of the rare-earth ions. By means of a general model endowed with only the necessary elements from the crystal structure, we show how umbrella-like spin structures can take place and calculate the canting-angle as a result of the competition between the exchange-interaction of the rare-earth and the iron ions as well as the crystal-field anisotropy. Our results are compared to experimental data, and a study of the polarised spin wave dynamics is presented. Our study improves the understanding of umbrella-like spin structures and paves the way for more complex spin wave calculations in rare-earth iron garnets with non-collinear magnetic phases.(c) 2022 Elsevier Inc. All rights reserved.

Automated summary

Rare-earth iron garnets are important materials for spintronic devices. This study investigates the formation mechanism of umbrella-like spin structures in these garnets and explores the polarized spin wave dynamics. The findings improve the understanding of non-collinear magnetic phases in rare-earth iron garnets.