thank you for initiating this interesting discussion on RG. In order to provide you with useful information it would grately help if you could clarify a few points first. For example, it would help if you could specify which manganese nitrides you have in mind. I know of at least three different manganese nitrides, namely MnN, Mn2N3, and Mn4N (there are certainly more). Then there are various preparative techniques available to manufacture manganese nitrides both as bulk material and as thin films. For some initial information please have a look at the following interesting presentation: