[Paper Review] Manipulating chiral-spin transport with ferroelectric polarization

Xiaoxi Huang, Xianzhe Chen+29 more|arXiv (Cornell University)|Jun 3, 2023

Multiferroics and related materials4 citations

TL;DR

This paper demonstrates electric-field control of chiral-spin transport in multiferroic BiFeO₃ via ferroelectric polarization reversal, enabling up to 18% rectification of magnon currents at room temperature. The spin torque from magnons efficiently switches adjacent magnetic layers, enabling all-oxide, energy-scalable logic with ferroelectrically gated magnon propagation.

ABSTRACT

A collective excitation of the spin structure in a magnetic insulator can transmit spin-angular momentum with negligible dissipation. This quantum of a spin wave, introduced more than nine decades ago, has always been manipulated through magnetic dipoles, (i.e., timereversal symmetry). Here, we report the experimental observation of chiral-spin transport in multiferroic BiFeO3, where the spin transport is controlled by reversing the ferroelectric polarization (i.e., spatial inversion symmetry). The ferroelectrically controlled magnons produce an unprecedented ratio of up to 18% rectification at room temperature. The spin torque that the magnons in BiFeO3 carry can be used to efficiently switch the magnetization of adja-cent magnets, with a spin-torque efficiency being comparable to the spin Hall effect in heavy metals. Utilizing such a controllable magnon generation and transmission in BiFeO3, an alloxide, energy-scalable logic is demonstrated composed of spin-orbit injection, detection, and magnetoelectric control. This observation opens a new chapter of multiferroic magnons and paves an alternative pathway towards low-dissipation nanoelectronics.

Motivation & Objective

• To demonstrate electric-field manipulation of chiral-spin transport in multiferroic BiFeO₃ using ferroelectric polarization.
• To achieve room-temperature, controllable magnon-mediated spin transport with high efficiency.
• To develop an all-oxide, energy-scalable logic architecture based on ferroelectrically controlled magnon propagation.
• To quantify spin-torque efficiency and nonlocal spin transport in BiFeO₃/SrIrO₃ heterostructures.

Proposed method

• Utilized lateral nonlocal spin transport measurements with spin-orbit injection and detection via Pt and SrIrO₃ wires on BiFeO₃ films.
• Applied in-plane electric field pulses to switch ferroelectric polarization and modulate magnon current, with voltage signals measured over 100 seconds.
• Employed spin Hall effect (first-harmonic voltage) and spin Seebeck effect (second-harmonic voltage) to generate and detect magnons.
• Measured hysteretic, butterfly-shaped voltage responses correlated with ferroelectric domain switching, confirming polarization control.
• Fitted distance-dependent nonlocal voltage signals to the diffusive magnon propagation model: $ R_{ m{nl}} = rac{C}{ ho} rac{ m{exp}(d/ ho)}{1 - m{exp}(2d/ ho)} $, yielding diffusion lengths of ~0.17 μm and ~0.25 μm.
• Calculated inverse spin-Hall voltage using $ V_{ m{ISHE}} = rac{ heta_{ m{SOT}} ho_{ m{SD}} anh(t_{ m{SIO}}/(2 ho_{ m{SD}})) L}{t_{ m{SIO}} ho_{ m{SIO}}} J_{ m{S}} $, predicting ~10 mV output for 10 nm BiFeO₃ thickness.

Experimental results

Research questions

• RQ1 Can ferroelectric polarization reversal control chiral-spin transport in multiferroic BiFeO₃ at room temperature?
• RQ2 What is the efficiency of magnon-induced spin torque in switching adjacent magnetic layers in BiFeO₃/SrIrO₃ heterostructures?
• RQ3 How does the nonlocal magnon current depend on ferroelectric domain state and electrode spacing?
• RQ4 Can ferroelectrically controlled magnon transport enable scalable, all-oxide spintronic logic devices?
• RQ5 What is the predicted output voltage of a vertical magnon-based MESO device using BiFeO₃ with SrIrO₃ as spin detector?

Key findings

• Ferroelectric polarization reversal in BiFeO₃ induces a rectification ratio of up to 18% in magnon transport at room temperature.
• The critical switching current for magnetization reversal in SrRuO₃ is lower under upward ferroelectric polarization, indicating higher spin transmission efficiency.
• Nonlocal voltage signals in BiFeO₃/SrIrO₃ exceed those in BiFeO₃/Pt by approximately one order of magnitude (~1 μV vs. ~0.1 μV).
• Distance-dependent nonlocal signals fit the diffusive magnon propagation model with effective diffusion lengths of ~0.17 μm (spin Hall-driven) and ~0.25 μm (thermally driven).
• Theoretical modeling predicts an inverse spin-Hall voltage of ~10 mV for a 10 nm BiFeO₃ thickness, approaching the MESO target of 100 mV.
• Hysteretic, butterfly-shaped voltage responses confirm robust, electrically controllable magnon transport with coercive fields matching ferroelectric switching.