Magnetic domain structures and magnetotransport properties in Co-Ag granular thin films

The magnetic microstructures and magnetotransport properties in granular Co -x,Ag1-x films with 17% less than or equal to x less than or equal to 62% w ere studied. Magnetic force microscopy (MFM) observations showed the presen ce of magnetic stripe domains in as-deposited samples with x greater than o r equal to 45% and the evolution of the magnetic domain patterns to in-plan e domains with annealing. A perpendicular magnetic anisotropy as high as ab out 8 x 10(5) ergs/cc for as-deposited Co62Ag38 and about 6 x 10(5) ergs/cc for as-deposited Co45Ag55 was observed by magnetization and torque measure ments. With increasing annealing temperature, the perpendicular magnetic an isotropy became negative. The origin of the perpendicular magnetic anisotro py may be attributed to a rhombohedral distortion of the cubic cell due to residual substrate-film stresses. The magnetic stripe domains are the conse quence of the interplay of the indirect or direct exchange, perpendicular m agnetic anisotropy and dipolar interactions. Finally, magnetoresistance (MR ) curves displayed training behaviours and different shapes when measured w ith different configurations (parallel, transverse and perpendicular). It i s proposed that the existence and the evolution of the magnetic domain stru ctures strongly affect the magnetotransport properties due to the extra con tribution of the electron scattering at the domain walls. Furthermore, an a nisotropic MR also contributes to the overall MR curves.