Abstract
<title>Abstract</title> <p>Liquid crystals (LCs) provide a canonical framework to understand intermediate phases between liquids and crystals, such as nematic and smectic order, and the rich phenomenology that emerges when such orders are subjected to boundaries, confinement, and elastic frustration. Here, we reveal a hidden mesoscale liquid-crystal-like organization of spin cycloids in a room-temperature magnetoelectric antiferromagnet BiFeO3. It is observed that ferroelectric domain walls act as anchoring surfaces, locally selecting cycloid propagation vectors analogous to surface induced alignment in LCs. Interestingly, confinement imposed by multiple domain walls stabilizes coherent smectic-like cycloidal order in between domain walls through “order by confinement”, while geometrical frustration at domain boundaries induces non-local Helfrich-Hurault–type elastic instabilities in cycloid smectics. Building on these insights, we show that surface-energy engineering dramatically enhances the long range orientational coherence of spin cycloids, enabling robust non-local magnon transport in the ultra-thin limit. These findings establish self-organization as a guiding principle for engineering novel magnetic textures and emergent spin functionalities, opening new opportunities for spintronic and magnonic technologies.</p>