Domain observation and transition from giant magnetoresistance to anisotropy magnetoresistance in Ag<inf>1-x</inf>(Ni<inf>0.8</inf>Co<inf>0.2</inf>)<inf>x</inf> granular films

Abstract

A series of Ag1-x(Ni0.8Co0.2)x granular film samples were prepared using an ion-beam cosputtering technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were performed to investigate the microstructure of these samples. The results measured using a vibrating sample magnetometer (VSM) show a gradual change from superparamagnetism to ferromagnetism as x increases in these samples. Magnetoresistance was measured using a conventional four terminal method at room temperature. As x increases, a transition from giant magnetoresistance (GMR) to anisotropic magnetoresistance (AMR) has been observed. The stripe-type domains have been observed using magnetic force microscopy (MFM) in the high x samples, and the domains gradually disappear as x decreases. It suggests that the transition from GMR to AMR may result from intergranular interaction (not only dipolar) in the samples as x increases. © 2003 Elsevier Ltd. All rights reserved.