Magnetic nitrides and magnetic heterostructures have attracted considerable attention due to their potential importance to magnetic sensor technology. This project investigates the growth, electronic, magnetic properties of magnetic manganese nitride and manganese nitride based magnetic heterostructures.
A series of magnetic materials have been studied. It is composed of three types of magnetic systems: magnetic nitride-manganese nitride, ferromagnetic metal on antiferromagnetic nitride - Fe/Mn3N2; and ferri-magnetic nitride on nitride semiconductor – Mn4N/GaN. These magnetic materials have been grown by molecular beam epitaxy and investigated with various analytical tools. Reflection high energy electron diffraction and X-ray diffraction are used to determine the structures of these materials and their epitaxial relationship with the substrates.
Scanning tunneling microscopy is used to study the phase transformation of a thin manganese nitride film, the well-ordered array of MnN-bonded Mn-tetramer clusters on Mn3N2 (001) surface, the step structures and morphology of Mn3N2 (010) surface and Fe thin films on Mn3N2 (010). The row-wise antiferromagnetic Mn3N2 (010) surface has been investigated using spin-polarized scanning tunneling microscopy. It is shown that the magnetic contrast in atomic-scale images is a strong function of the bias voltage around the Fermi level.
Atomic force microscopy is also used to investigate the morphology of Fe films on Mn3N2 (010) and Mn4N thin films on GaN(0001).