Nanoparticle morphology in FeNi–Cu granular films with giant magnetoresistance

A series of (Fe 50 Ni 50 ) x Cu 1− x granular films were prepared using the magnetron-controlled sputtering method. The nanoparticle morphology and giant magnetoresistance (GMR) of FeNi–Cu films deposited at room temperature were investigated through the transmission electron microscope (TEM) and the conventional four probes method under room temperature, respectively. Upon varying the magnetic volume fraction x , the GMR of as-deposited FeNi–Cu films reached a maximum of about 1.8% at a volume fraction of 32% FeNi. In addition, TEM observation disclosed that FeNi–Cu films consist of FeNi nanoparticles dispersed in Cu matrix and form FCC structure. For films with lower volume fraction of FeNi particles, the size distribution of FeNi particles satisfied a log-normal function. With increasing volume fraction of FeNi particles, the size distribution of FeNi particles deviated gradually from a log-normal function. Meanwhile, the average size of FeNi particles increased monotonically with increasing volume fraction of FeNi particles, leading to the fact that GMR can reach a peak value at a certain middle particle size. In addition, the relationship between GMR and nanoparticle morphology of granular films was discussed.