Surface and bulk magnetic anisotropy in bilayered CoSiB/FeNbCuSiB and FeNbSiB/FeSiB ribbons

• CoSiB/FeNbCuSiB and FeSiB/FeNbSiB alloys prepared by the planar flow casting method.
• Amorphous structure of both ribbons confirmed by XRD and SEM.
• Bulk magnetic properties influenced mainly by the Fe-rich air sides.
• λs of single layers determines surface magnetic anisotropy induced due to coiling.
• Bulk magnetic anisotropy detects integral properties of both layers and interface.

The present study is devoted to the surface and bulk magnetic anisotropy of the bilayered Co72.5Si12.5B15/Fe73.5Nb3Cu1Si13.5B9 and Fe74.5Nb3Si13.5B9/Fe77.5Si7.5B15 ribbons which, completed with microstructure analysis, give the basic complex data prospectively usable for sensor applications. The ribbons prepared by modernized planar flow casting technology were fully amorphous as the X-ray diffraction measurements have confirmed. The thickness of ribbons was about 36 μm while the interlayer thickness reaches typically a few μm as the element distributions at cross-sections have shown. A bending of ribbons leads to changes in both surface and bulk anisotropies detected by the magneto-optical Kerr effect and vibrating sample magnetometer, respectively. An observable difference between both anisotropies is ascribed to the fact that the surface magnetic anisotropy is determined only by magnetostrictive behavior of the corresponding individual layer while the bulk anisotropy depends on integral properties of both layers and the interlayer. Moreover, the magnetic measurements at room and elevated temperatures have shown that the bulk magnetic properties are more markedly influenced by the composition of iron rich layers, FeSiNbCuB or FeSiB, being during the casting in contact with air.