Compositional Variations of Co-based Thin films for Biasing Magnets in GMR/TMR Read Heads

摘要

Co-based thin-film permanent magnets are used for magnetic field biasing in GMR read heads. The use of biasing improves performance and reduces noise in the sensor. The composition of the biasing magnets is similar to that of longitudinal recording media (CoCrPt). It has been well known that in media films deposited at elevated temperature, Cr segregates to grain boundaries and decouples magnetic interactions between grains and thus suppresses noise level [1, 2]. On the other hand, there is no previous evidence for segregation of Pt [3]. In this work, a combination of several techniques has been used to characterise two Co-based thin films of nominal composition Co{sub}70Cr{sub}10Pt{sub}20 deposited on Cr seed layers. Both seed and film were deposited at different angles, 0 or 25 degrees to the film normal. The films were deposited by ion beam deposition (IBD) at room temperature. The magnetic measurements show that the coercivity is increased for the higher deposition angle in agreement with the previous investigation[4]. Furthermore, from stress measurement, the stress is lower with the films deposited at a larger angle.