Strongly Enhanced Gilbert Damping in 3d Transition Metal Ferromagnet Monolayers in Contact with Topological Insulator Bi2Se3

TL;DR

This paper theoretically investigates how contact with topological insulator Bi2Se3 significantly enhances the Gilbert damping in 3d transition metal ferromagnetic monolayers, offering a new way to control damping in spintronic devices.

Contribution

It extends the scattering theory of Gilbert damping using a torque method to predict enhanced damping in ferromagnetic monolayers contacted with topological insulators.

Findings

Gilbert damping is increased by about ten times in contact with Bi2Se3.

Strong spin-orbit coupling in Bi2Se3 causes the damping enhancement.

The method provides a way to tailor damping in ferromagnetic films.

Abstract

Engineering Gilbert damping of ferromagnetic metal films is of great importance to exploit and design spintronic devices that are operated with an ultrahigh speed. Based on scattering theory of Gilbert damping, we extend the torque method originally used in studies of magnetocrystalline anisotropy to theoretically determine Gilbert dampings of ferromagnetic metals. This method is utilized to investigate Gilbert dampings of 3d transition metal ferromagnet iron, cobalt and nickel monolayers that are contacted by the prototypical topological insulator Bi2Se3. Amazingly, we find that their Gilbert dampings are strongly enhanced by about one order in magnitude, compared with dampings of their bulks and free-standing monolayers, owing to the strong spin-orbit coupling of Bi2Se3. Our work provides an attractive route to tailoring Gilbert damping of ferromagnetic metallic films by putting them in contact with topological insulators.