Structural characterization and magnetic properties of L10-MnAl films grown on different underlayers by molecular beam epitaxy.

We grow MnAl films on different underlayers by molecular beam epitaxy (MBE), and investigate their structural and magnetic properties. L 1 0 -ordered MnAl films were successfully grown both on an MgO(0 0 1) single-crystalline substrate and on an Mn 4 N(0 0 1) buffer layer formed on MgO(0 0 1) and SrTiO 3 (0 0 1) substrates. For the MgO substrate, post rapid thermal annealing (RTA) drastically improved the crystalline quality and the degree of L 1 0 -ordering, whereas no improvement in the crystallinity was achieved by altering the substrate temperature ( T S ) during MBE growth. However, high-quality L 1 0 -MnAl films were formed on the Mn 4 N buffer layer by simply varying T S . Structural analysis using X-ray diffraction showed MnAl on an MgO substrate had a cubic structure whereas MnAl on the Mn 4 N buffer had a tetragonal structure. This difference in crystal structure affected the magnetic properties of the MnAl films. The uniaxial magnetic anisotropy constant ( K u ) was drastically improved by inserting an Mn 4 N buffer layer. We achieved a perpendicular magnetic anisotropy of K u  = 5.0 ± 0.7 Merg/cm 3 for MnAl/Mn 4 N film on MgO and 6.0 ± 0.2 Merg/cm 3 on STO. These results suggest that Mn 4 N has potential as an underlayer for L 1 0 -MnAl. [ABSTRACT FROM AUTHOR]