Nonreciprocal spin-charge interconversion in topological insulator/ferromagnet heterostructures

Abstract

The process of spin-charge interconversion is critical in modern spintronics. Nonetheless, experiments conducted on a wide variety of magnetic heterostructures consistently report that charge-to-spin and spin-to-charge conversion efficiencies can be vastly different, especially in the case of topological insulators (TI). This discrepancy between the two "reciprocal" effects remains unexplained, hampering the development of spin devices based on spin-charge conversion. In this study, we investigate both spin-charge and charge-spin interconversion processes in TI Bi2Te3/Py and Pt/Py bilayers experimentally using spin-torque ferromagnetic resonance and spin pumping techniques. We find that the measured charge-to-spin conversion efficiency (C-S) in TI/Py is ~26 times larger than the measured spin-to-charge conversion efficiency (S-C), whereas C-S and S-C are comparable in the case of Pt/Py. Using a theoretical model enforcing Onsager reciprocity, we show that spin-to-charge and charge-to-spin conversions in bilayers are genuinely inequivalent, and explain our results as arising from the distinct spin current leakage that takes place during the interconversion. This work clarifies previous conflicting reports on spin-charge interconversion processes and highlights the potential of interface engineering to achieve efficient spin transport in TI-based ferromagnetic heterostructures, paving the way for highly efficient spintronic devices.

4 figures

References in corpus (15)

• Spin Torque Ferromagnetic Resonance Induced by the Spin Hall Effect
• Spin Transfer Torque Generated by the Topological Insulator Bi_2Se_3
• Quantifying spin Hall angles from spin pumping: Experiments and Theory
• Detection and quantification of inverse spin Hall effect from spin pumping in permalloy/normal metal bilayers
• Fermi level dependent charge-to-spin current conversion by Dirac surface state of topological insulators
• Room temperature magnetization switching in topological insulator-ferromagnet heterostructures by spin-orbit torques
• Determination of intrinsic spin Hall angle in Pt
• First-principles study of magnetization relaxation enhancement and spin-transfer in thin magnetic films
• Surface state dominated spin-charge current conversion in topological insulator/ferromagnetic insulator heterostructures
• Effective spin-mixing conductance of heavy-metal-ferromagnet interfaces
• Observation of inverse spin Hall effect in bismuth selenide
• Dependence of spin pumping spin Hall effect measurements on layer thicknesses and stacking order
• Extremely large non-saturating magnetoresistance and ultrahigh mobility due to topological surface states in metallic Bi2Te3 topological insulator
• Role of spin mixing conductance in spin pumping: enhancement of spin pumping efficiency in Ta/Cu/Py structures
• Planar Hall effect induced spin rectification effect and its strong impact on spin pumping measurements

Cited by in corpus (2)

• Interface controlled Berry phase and anisotropic spin-charge conversion in altermagnet-topological insulator bilayers
• Impact of the out-of-plane conductivity on spin transport evaluation in a van der Waals material