  In this work we are investigating the effect of strain in ultrathin Mn-Ga
thin films on the magnetic properties at room temperature. Two different Mn-Ga
compositions of which one is furthermore doped with Co were grown on Cr
buffered MgO (001) substrates. Films with a thickness below 12nm are highly
strained and it was observed that the ratio c/a vs. thickness is depending on
composition. Using c/a as an order parameter the PMA is shown to be drastically
reduced with increasing strain. These findings should be considered when
generalizing and downscaling results obtained from films >20nm. Furthermore it
has been shown, that the strain can be reduced by introducing an additional Pt
buffer and thus maintaining a high PMA for a thickness as low as 6nm.
