Spin ordering in Fe3-x Mn x Si Heusler alloys

Applying the augmented spherical wave method, the Heusler alloy Fe3-x Mn x Si is studied for integer values of x where it forms fairly well ordered intermetallic compounds. In our calculation we allow for non-collinear spin ordering. It is found that the magnetic ground state changes from a ferromagnet for Fe3Si to a long wavelength spin spiral for Mn3Si which is close to a [111] antiferromagnet. Our results are in excellent agreement with experiment, which is particularly true for Fe2MnSi where our calculations confirm the experimental conjecture of a [111] antiferromagnet with a ferromagnetic component due to a canting of the spins off the [111] axis.