Strain engineering of the magnetic multipole moments and anomalous Hall effect in pyrochlore iridate thin films

A recent observation of anomalous Hall Effect (AHE) in antiferromagnets has suggested that the ferromagnetic ordering is not a necessary condition. Accordingly, a theoretical study showed that higher-rank multipoles formed by a cluster of spins (cluster multipoles) can generate the anomalous Hall Effect without magnetization. Despite such an intriguing proposal, it has seldom been investigated to control the unconventional AHE by including the cluster multipoles. Here, we demonstrate that a strain can manipulate the hidden Berry curvature effect by inducing the higher-order cluster multipoles in spin-orbit-coupled antiferromagnets. Observing the large AHE on fully strained antiferromagnetic Nd₂Ir₂O₇ thin films, we prove that strain-induced cluster T₁-octupoles are the only source of observed AHE. Our results provide a previously unidentified pathway for generating the unconventional AHE via strain-induced magnetic structures and establish a platform for exploring undiscovered topological phenomena via strain in correlated materials.