Sliding Ferroelectricity Driven Spin‐Layertronics in Altermagnetic Multilayers

ABSTRACT The synergy of ferroicity with altermagnetism offers a novel platform for designing multifunctional altermagnetic‐spintronic device technology. In this work, we propose a mechanism to achieve nonvolatile electrical manipulation of spin and layer degrees of freedom in an altermagnetic bilayer via sliding ferroelectricity. Using first‐principles calculations, we show that an interlayer translation can induce a switchable out‐of‐plane ferroelectric polarization in bilayer CuF ₂ , which directly couples to and reverses the d ‐wave altermagnetic spin splitting. Notably, the altermangetic spin splitting is layer‐locked, the sliding ferroelectricity‐driven switching thus embodying a nonvolatile spin‐layertronics functionality that couples spin‐polarized transport and layer degree of freedom in a single platform. We show that in quadrilayer CuF ₂ , four polarization states are identified which may offer multi‐state logic device applications. These findings establish sliding ferroelectricity as a versatile tool for designing voltage‐controlled, high‐speed, and energy‐efficient spin‐layertronic devices based on altermagnets.