KNbO3-based multiferroic heterostructures: a lead-free alternative for strain-driven magnetic modulations

Artificial multiferroic heterostructures offer a versatile platform for engineering magnetic properties through interfacial strain and magnetoelectric coupling. In this framework, we demonstrate the growth of both Ni and Lao.67Sro.33MnO3 ferromagnetic thin films on KNbO3 (100) single crystals. We show, by combining structural and magneto-optical characterizations, how their magnetic responses are affected by the structural transitions taking place in the substrate as a function of temperature. In particular, we observe sensitive modifications in the ferroelectric domain composition of KNbO3, especially after cooling from orthorhombic to rhombohedral phase, leading to a transition from in-plane anisotropic to isotropic magnetization behaviour in Ni-thin films. Temperature dependent magnetic characterizations show a coercivity modulation while crossing the structural transition for both Ni and Lao.67Sro.33MnO3 films, signature of interfacial strain-driven coupling. To the best of our knowledge, these are the first reported KNbO-based multiferroic heterostructures, establishing this lead-free material as a potential functional host for both metallic magnetostrictive and complex oxide thin films