Room-temperature negative magnetoresistance of FeCo- diamond like carbon nanocomposite film with high anticorrosion and antibiosis

Magnetic metal (Co, Fe, etc.)-diamond like carbon (DLC) nanocomposite film is promising for implantable magnetoresistance biosensor material, which requires room temperature (RT) tunneling magnetoresistance (TMR), high anticorrosion and antibiosis, simultaneously. However, carbonization of magnetic metals reduces saturation magnetization of films, which is a critical problem for realizing RT-TMR. In this study, introduction of FeCo alloy can effectively inhibit formation of Co carbides, which makes FeCo-DLC film has high saturation magnetization from 0.125 to 0.284 T, as FeCo content increasing from 45 to 64 at.%. Moreover, tunneling conduction paths of uniformly distributed FeCo particles have been obtained by sputtering-pressure controlling. Consequently, RT-TMR of -0.01% is innovatively realized in FeCo-DLC nanocomposite films. For anticorrosion, the microporous is the main cause of low corrosion resistance. Owing to microporous blocking effect of sp² cluster enhanced by FeCo alloy, corrosion resistance of FeCo-DLC film reaches 2.5×10⁵ Ω⋅cm², which is 10 times higher than that of Co-DLC films. Meanwhile, as FeCo content increasing, higher sp²/sp³ ratio can reduce surface energy, and enhance hydrophobicity to prevent bacteria adsorption. Antibacterial rate exhibits significant increase from 59 to 92%. Integration of the multiple properties is realized in FeCo-DLC nanocomposite film for biosensor material.