Dislocation structures, interfacing, and magnetism in the L10-MnGa on η ⊥-Mn3N2 bilayer

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© 2019 Author(s). Ferromagnetic L10-MnGa was grown by molecular beam epitaxy under ultrahigh vacuum conditions to a 73±5nm thickness atop of 50±5nm thick molecular beam epitaxy grown antiferromagnetic η⊥-Mn3N2 on an MgO(001) substrate. The MnGa grew along the c-axis with an out-of-plane spacing of c=3.71±0.01Å and a relaxed in-plane spacing of a=4.00±0.05Å measured with x-ray diffraction and reflection high-energy electron diffraction, respectively. Williamson-Hall analysis revealed 67±17nm tall columnar grains with a residual strain of 2.40±0.26(×10-3). A radial distribution plot of screw dislocations observed in scanning tunneling microscopy images showed an in-plane coherence length of 15±5nm. Reflection high-energy electron diffraction analysis of the in-plane lattice spacing during growth reveals a critical thickness of 1.05±0.65nm for the MnGa, after which the MnGa film relaxes by incorporating dislocations of both edge and screw type. Vibrating sample magnetometry was employed to obtain the magnetic properties of the bilayer system. It is found that the dislocation density plays a significant role in influencing the measured moment per unit cell, where a large dislocation density lowers the moment per unit cell significantly due to chemical layer disordering.