Structural and magnetic properties of CoNi surface alloys

Abstract The surface alloys were deposited on Si (100) substrate by dc-magnetron sputtering technique and were investigated using Grazing Incidence X-ray Diffraction (GIXRD), X-ray reflectivity (XRR), Energy dispersive X-ray analysis (EDAX) and Magneto-Optical Kerr Effect (MOKE) measurements. GIXRD measurements suggested a compositional induced structural transition from hcp to fcc structure at x = 40. MOKE measurements indicate that the prepared alloys are soft ferromagnet with the coercive field in the range of few mT. The MOKE microscopy domain image suggests that magnetization reversal occurring through domain wall motion and coherent rotation. The angle-dependent coercivity (H c ) is numerically fitted with a two-phase model of magnetization reversal. Large anisotropy dispersion is observed for hcp Co-Ni alloys compared to fcc Co-Ni alloys. The hcp Co 80 Ni 20 alloy has highest value of coercivity at 0 o but for fcc Co 60 Ni 40 and Co 40 Ni 60 alloys, the coercivity became highest at 120 o . The magnetization reversal along hard axis occurs through coherent rotation for fcc Co 60 Ni 40 and Co 40 Ni 60 alloys whereas in hcp Co 80 Ni 20 alloy magnetization reversal is governed by formation of fine domains.