Perpendicular magnetic anisotropy, hysteresis and structural properties of nanostructured FeCoV/Ti multilayers

FeCoV/Ti multilayers are investigated in order to study perpendicular magnetic anisotropy, variation of saturation magnetization, remanence, coercivity and structural properties. Five samples with t_Ti=1.04 nm and t_FeCoV=0.89-4.47 nm are prepared by DC magnetron sputtering. X-ray diffraction measurements carried out on the samples show a strong FeCoV(1 1 0) texture for larger t_FeCoV. The grain size determined from the FeCoV(1 1 0) peaks displays a decreasing trend with decreasing t_FeCoV indicating that the grain size is mainly determined by the t_FeCoV. We have performed magnetic hysteresis measurements in order to investigate various magnetic properties. The interface/surface and volume anisotropy constants determined from the measurements are K_s=0.826 mJ/m² and K_v=-1.84 MJ/m³, respectively. The data analysis indicates that the samples may have their easy direction of magnetization perpendicular to the film plane for t_FeCoV<0.89 nm.The saturation magnetization is observed to decrease with decreasing t_FeCoV and from a plot of M_st_FeCoV vs. t_FeCoV we have determined a dead layer thickness of 0.33 nm at the FeCoV interfaces. The variation of coercivity and remanence with t_FeCoV may be due to both random anisotropy and superparamagnetism. The decrease in remanence with decreasing t_FeCoV can also be attributed to the progressive change of the easy direction of magnetization away from the film plane.