Dislocation structures, interfacing, and magnetism in the L1 0 - MnGa on η ⊥ - Mn 3 N 2 bilayer
Ferromagnetic L1 0 -MnGa was grown by molecular beam epitaxy under ultrahigh vacuum conditions to a 73 ± 5 nm thickness atop of 50 ± 5 nm thick molecular beam epitaxy grown antiferromagnetic η ⊥ -Mn 3 N 2 on a MgO(001) substrate. The MnGa grew along the c-axis with an out-of-plane spacing of c = 3.71 ± 0.01 Å and a relaxed in-plane spacing of a = 4.00 ± 0.05 °A measured with X-ray diffraction and reflection high-energy electron diffraction respectively. Williamson-Hall analysis revealed 67 ± 17 nm tall columnar grains with a residual stress of 2.40 ± 0.26 (×10 -3 ). A radial distribution plot of screw dislocations observed in scanning tunneling microscopy images found an in-plane coherence length of 15 ± 5 nm. Reflection high-energy electron diffraction analysis of the in-plane lattice spacing during growth reveals a critical thickness of 1.05 ± 0.65 nm for the MnGa, by 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 understanding the measured moment per unit cell, where a large dislocation density lowers the moment per unit cell significantly due to chemical layering disorder. Finally, this finding is important for materials development of large saturation magnetization.