Target-Substrate Distance Dependences of GMR and Microstructure in Fe_xCo_1-x-Al₂O₃ Granular Thin Films

Abstract

The magnetic properties and magnetoresistance of Fe_xCo_1-x-Al₂O₃ thin films were studied by changing the target-substrate distance (D_T-S) from 65 to 120 mm. The films were prepared by rf magnetron sputtering. The MR ratio of Fe_0.2Co_0.8-Al₂O₃ thin films increased with increasing D_T-S. An MR ratio of 7.3% was obtained in a film with D_T-S of 120 mm at room temperature. The MR ratio and the MR sensitivity of Fe_xCo_1-x-Al₂O₃ thin films exhibited a maximum at about x = 0.2. From an analysis of the structure, it is considered that the enhancement of the MR ratio is related to enlargement and small distribution of the macroscopic grain size in the films.