Experimental investigation of the effect of topological insulator on the magnetization dynamics of ferromagnetic metal: BiSbTe_1.5Se_1.5 and Ni₈₀Fe₂₀ heterostructure

2023/03/13 by Sayani Pal, Pal, Sayani, Soumik Aon +9
Materials Science · Physics and Astronomy · #FOS: Physical sciences #Graphene research and applications #Magnetic properties of thin films #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Topological Materials and Phenomena

paper · pdf · doi:10.48550/arxiv.2303.07025

openalex publication_date 2023/03/13 · openalex created_date 2023/03/16 · openalex updated_date 2026/07/28

Abstract

We have studied ferromagnetic metal/topological insulator bilayer system to understand magnetization dynamics of ferromagnetic metal (FM) in contact with a topological insulator (TI). At magnetic resonance condition, the precessing magnetization in the metallic ferromagnet (Ni₈₀Fe₂₀) injects spin current into the topological insulator (BiSbTe_1.5Se_1.5), a phenomenon known as spin-pumping. Due to the spin pumping effect, fast relaxation in the ferromagnet results in the broadening of ferromagnetic resonance linewidth (ΔH). We evaluated the parameters like effective Gilbert damping coefficient (α_eff), spin-mixing conductance (g_eff^{\uparrow \downarrow}) and spin current density (j_S⁰) to confirm a successful spin injection due to spin-pumping into the BiSbTe_1.5Se_1.5 layer. TIs embody a spin-momentum locked surface state that span the bulk band-gap. It can act differently to the FM magnetization than the other normal metals. To probe the effect of topological surface state, a systematic low temperature study is crucial as surface state of TI dominates at lower temperatures. The exponential growth of ΔH for all different thickness combination of FM/TI bilayers and effective Gilbert damping coefficient (α_eff) with lowering temperature confirms the prediction that spin chemical bias generated from spin-pumping induces surface current in TI due to spin-momentum locking. The hump-like feature of magnetic anisotropy field (H_K)of the bilayer around 60K suggests that the decrease of interfacial in-plane magnetic anisotropy can result from exchange coupling between the TI surface state and the local moments of FM layer.

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