This work demonstrates dramatically modified spin dynamics of magnetic insulator (MI) by the spin-momentum locked Dirac surface states of the adjacent topological insulator (TI) which can be harnessed for spintronic applications. As the Bi-concentration x is systematically tuned in 5 nm thick (BixSb1-x)2Te3 TI film, the weight of the surface relative to bulk states peaks at x = 0.32 when the chemical potential approaches the Dirac point. At this concentration, the Gilbert damping constant of the precessing magnetization in 10 nm thick Y3Fe5O12 MI film in the MI/TI heterostructures is enhanced by an order of magnitude, the largest among all concentrations. In addition, the MI acquires additional strong magnetic anisotropy that favors the in-plane orientation with similar Bi-concentration dependence. These extraordinary effects of the Dirac surface states distinguish TI from other materials such as heavy metals in modulating spin dynamics of the neighboring magnetic layer.
@article{arxiv.1806.00151,
title = {Dirac-Surface-State Modulated Spin Dynamics in a Ferrimagnetic Insulator at Room Temperature},
author = {Chi Tang and Qi Song and Cui-Zu Chang and Yadong Xu and Yuichi Ohnuma and Mamoru Matsuo and Yawen Liu and Wei Yuan and Yunyan Yao and Jagadeesh S. Moodera and Sadamichi Maekawa and Wei Han and Jing Shi},
journal= {arXiv preprint arXiv:1806.00151},
year = {2018}
}