LAUSR

Magnon spin current, which delivers spin angular momentum without charge flow, has garnered considerable interest for next‐generation spintronic applications. Antiferromagnetic insulators have been shown to be the ideal material platform for magnonics. However, it remains a challenge to effectively control the antiferromagnetic magnon transport. Here, the control over both transmissivity and anisotropy of antiferromagnetic magnon transport in magnetic multilayers is reported, achieved through the delicate interplay between interfacial coupling and magnetocrystalline anisotropy. In La0.7Sr0.3MnO3 (LSMO)/LaFeO3 (LFO)/Pt heterostructures, a Néel vector reorientation as temperature decreases is observed through soft X‐ray magnetic linear dichroism. Temperature‐ and angular‐dependent spin pump data reveal three regions with distinct antiferromagnetic magnon transport characteristics, evolving from a magnon‐conducting state with uniaxial anisotropy to an intermediate state with reduced transmissivity and weak anisotropy, and ultimately to a magnon‐insulating state. Theoretical modeling reveals that this modulation is likely attributed to the evolution of both antiferromagnetic axis and domain structure of LFO, determined by the competition between exchange coupling across the interface and the intrinsic magnetic anisotropy of LFO. These findings provide fundamental insights into the critical role of the interface in controlling the magnon transport in magnetic multilayers and offer a new toolkit for developing magnonic devices.