Non-collinear magnetism and exchange couplings in FeCo/Mn superlattices

We present the main results of a systematic study of the magnetic properties of Fe_xCo_{1 − x}/Mn_n for various Fe concentrations x and Mn thicknesses n. We show that the magnetic order in the Mn spacer changes from collinear to non-collinear when the Fe concentration decreases. This behaviour is discussed in relation with a bulk ‘canted’ magnetic state nearly degenerate with the collinear AF order. The origin of the exchange of stability between these two magnetic states is ascribed to a stronger collinear character of the Fe/Mn interface than the Co/Mn one.