Magnetic anisotropy of tetragonal FeCo/Pt(001) superlattices

The magnetic properties of tetragonally strained Fe0.36Co0.64 alloys in the form of FeCo/Pt(001) superlattices have been investigated experimentally. The strain was controlled by varying the individual constituent thicknesses in the range 3-10 atomic monolayers (ML), resulting in lattice-parameter ratios c/a between 1.18 and 1.31. The sample with a c/a ratio of 1.18 has a preferred out-of-plane magnetization direction and magnetic stripe domains, revealed by MFM, while samples with higher c/a ratios prefer in-plane magnetization. The strain-induced contribution to anisotropy was found to have a dominating effect. Saturation-magnetization values up to 2.31 T at room temperature were measured.