Bulk-Rashba Effect with Suppressed Spin Relaxation in a Polar Phase of Bi<sub>1-</sub> <sub>x</sub>In<sub>1+</sub> <sub>x</sub>O<sub>3</sub>.

Kang, Deokyoung; Lu, Xue-Zeng; Acharya, Megha; Husain, Sajid; Harris, Isaac; Behera, Piush; Lin, Ching-Che; Banyas, Ella et al. · Adv Mater · 2025

basic_science · Level V

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Abstract

The Rashba effect enables control over the spin degree of freedom, particularly in polar materials where the polar symmetry couples to Rashba-type spin splitting. The exploration of this effect, however, has been hindered by the scarcity of polar materials exhibiting the bulk-Rashba effect and rapid spin-relaxation effects dictated by the D'yakonov-Perel mechanism. Here, a polar LiNbO<sub>3</sub>-type R3c phase of Bi<sub>1-</sub> <sub>x</sub>In<sub>1+</sub> <sub>x</sub>O<sub>3</sub> with x ≈0.15-0.24 is stabilized via epitaxial growth, which exhibits a bulk-Rashba effect with suppressed spin relaxation as a result of its unidirectional spin texture. As compared to the previously observed non-polar Pnma phase, this polar phase exhibits higher conductivity, reduced bandgap, and enhanced dielectric and piezoelectric responses. Combining first-principles calculations and multimodal magnetotransport measurements, which reveal weak (anti)localization, anisotropic magnetoresistance, planar-Hall effect, and nonreciprocal charge transport, a bulk-Rashba effect without rapid spin relaxation is demonstrated. These findings offer insights into spin-orbit coupling physics within polar oxides and suggest potential spintronic applications.