Crystallographic Engineering for Enhanced Orbital Torque.

Spin currents and spin torques in magnetic structures have enabled nanoscale spintronic devices. Recent advances have revealed that their orbital counterparts─orbital currents and orbital torques─can be generated, opening the emerging field of orbitronics. However, harnessing orbital currents and orbital torques in solid-state devices remains a major challenge. Here, we demonstrate that crystal orientation engineering provides an effective route to control orbitronic devices. By investigating orbital torque in ferromagnets with epitaxially grown orbital current sources, we show that distinct crystal orientations between the ferromagnet and the orbital source markedly enhance torque efficiency. This counterintuitive result demonstrates that the enhanced efficiency arises from improved alignment between the momentum-space hotspots of orbital Berry curvature and those governing orbital transport. These findings highlight the importance of crystallographic engineering as a key strategy for advancing orbitronic devices and achieving a quantitative understanding of orbital transport and dynamics.