Orthogonal interlayer coupling in an all-antiferromagnetic junction.

In conventional ferromagnet/spacer/ferromagnet sandwiches, noncollinear couplings are commonly absent because of the low coupling energy and strong magnetization. For antiferromagnets (AFM), the small net moment can embody a low coupling energy as a sizable coupling field, however, such AFM sandwich structures have been scarcely explored. Here we demonstrate orthogonal interlayer coupling at room temperature in an all-antiferromagnetic junction FeO/CrO/FeO, where the Néel vectors in the top and bottom FeO layers are strongly orthogonally coupled and the coupling strength is significantly affected by the thickness of the antiferromagnetic CrO spacer. From the energy and symmetry analysis, the direct coupling via uniform magnetic ordering in CrO spacer in our junction is excluded. The coupling is proposed to be mediated by the non-uniform domain wall state in the spacer. The strong long-range coupling in an antiferromagnetic junction provides an unexplored approach for designing antiferromagnetic structures and makes it a promising building block for antiferromagnetic devices.