Magneto-optical imaging and coercivity mapping of GdFe spin-valve structures

Abstract

GdFe spin-valve structures, Si/bottom electrode/TbFeCo/CoFe (1 nm)/Cu (6 nm)/GdFe (10 nm)/Ru, with dimensions of 20×20 μm2 were investigated by a magneto-optical imaging technique. In a parallel configuration, i.e., a configuration in which the magnetization directions of GdFe and TbFeCo layers are parallel, the coercivity (Hc) decreases when nucleation centers are present in the patterns. In the antiparallel configuration, although few nucleation centers are present the deviation in Hc is greater than that in the parallel configuration.

Switching Field Distributions in GMR Patterns with GdFe Free Layers Obtained by High-resolution Magneto-optical Microscopy

“…We considered that the demagnetization field was not high in this case, because the GdFe layer had small saturation magnetization and was thin i.e., 16.5 nm. However, we attributed it to nucleation centers developed at the edge of the patterns, because the nucleation centers could have developed due to damages at the edges caused by the patterning process, resulting in the deterioration in the coercivity of the patterns 2) .…”

“…2, indicating that the GMR pattern used in this study has no severe defects or inhomogeneity resulting in magnetic nucleation centers. Figure 3 shows an optical and an MO image of GMR patterns with sizes of 200 200 nm 2 and 300 300 nm 2 measured with an applied magnetic field of 920 Oe. We observed patterns with a size of 200 200 nm 2 in the optical image.…”

“…We have reported the distributions of switching fields in GMR structures using the GdFe free layer. Although the origin of the distributions in the switching field was not clarified, MO imaging is one of the most effective techniques to study this 2) . Therefore, we applied this technique, to study the distribution origin.…”