Control of dynamic orbital response in ferromagnets via crystal symmetry

Transport of angular momentum is a key concept in condensed-matter physics. In solids, electrons can carry both spin and orbital angular momentum, leading to various applications in spintronics and orbitronics. A key difference between spin and orbital transport lies in their characteristic length scales in ferromagnets in which the dynamic orbital response is significantly long ranged compared with its spin counterpart. However, a comprehensive understanding of the physics behind the long-range nature of the orbital response is lacking. Here we demonstrate that the long-range dynamic orbital response in ferromagnets can be controlled by crystal symmetry. Our results manifest a clear difference in the characteristic length scale of orbital torque generation in atomically ordered and disordered CoPt alloys. This observation indicates that the long-range dynamic orbital response relies on the orbital-dependent energy splittings and hybridizations governed by crystal symmetry, which can be manipulated by atomic arrangements. Our results suggest the possibility of simultaneously controlling dynamic and static magnetic phenomena by manipulating orbital hybridization, which could be tailored for spintronic and orbitronic devices.