MR measurement of sub-micron scale relief structures fabricated in GMR materials

Understanding of magnetization process in patterned thin films is important for their applications in downsizing various magnetic devices. This paper deals with an experimental technique which enables us to characterize magnetization process in the ends of patterned ultra-thin films. In this study, only the top layer of magnetic sandwich structures were patterned into an array of fine magnetic particles using electron beam lithography and Ar ion milling to form relief structures in the films. The magnetization process of the arrays was inferred from magnetoresistance (MR) measurements of the films. MR behaviors of particle array samples of substrate/FM₁/Cu/FM₂ (FM₁, FM₂ = Co, NiFe, CoPt) in different pattern widths of ω = 0.2 and 0.6 μm, lengths L ranging from 0.2 to 280 μm and thicknesses of t = 6 and 18 nm were studied. From longitudinal MR measurements, a distinct decrease in remanent magnetization was found for sub-μm particle arrays, which may be associated with the formation of edge domains in the particles.