Probing antiferromagnetic coupling in magnetic insulator/metal heterostructures

The recent emergence of antiparallel interface coupling in hybrid ferromagnet metal/ferromagnetic insulator bilayers based on Y${}_{3}$Fe${}_{5}$O${}_{12}$ and NiFe raises questions about magnetic exchange coupling at this technologically important interface. A systematic study of heterostructures incorporating alternative ferromagnetic metals and a variety of substrates reveals that the antiparallel magnetic interaction is unique to heterostructures grown on amorphous SiO${}_{2}$, while multilayers on Gd${}_{3}$Ga${}_{5}$O${}_{12}$ or Gd${}_{3}$Ga${}_{5}$O${}_{12}$/Pt exhibit the traditional parallel exchange. X-ray diffraction implicates changes in the crystal order and orientation, which in a ferrimagnet such as Y${}_{3}$Fe${}_{5}$O${}_{12}$ may expose the minority spin lattice at the reconstructed interface for films on SiO${}_{2}$.