Epitaxial growth, structural characterization and exchange bias of non-collinear antiferromagnetic Mn${}_3$Ir thin films

Abstract

Antiferromagnetic materials are of great interest for spintronics. Here we present a comprehensive study of the growth, structural characterization, and resulting magnetic properties of thin films of the non-collinear antiferromagnet Mn${}_3$Ir. Using epitaxial engineering on MgO (001) and Al${}_2$O${}_3$ (0001) single crystal substrates, we control the growth of cubic ${\hat{I}}^3$-Mn${}_3$Ir in both (001) and (111) crystal orientations, and discuss the optimization of growth conditions to achieve high-quality crystal structures with low surface roughness. Exchange bias is studied in bilayers, with exchange bias fields as large as -29 mT (equivalent to a unidirectional anisotropy constant of 11.5 nJ cm${}^{-2}$) measured in Mn${}_3$Ir (111) / permalloy heterostructures at room temperature. In addition, a distinct dependence of blocking temperature on in-plane crystallographic direction in Mn${}_3$Ir (001) / Py bilayers is observed. These findings are discussed in the context of chiral antiferromagnetic domain structures, and will inform progress towards topological antiferromagnetic spintronic devices.

15 pages, 10 figures