Magnetic Properties of FePt based Nanocomposite Thin Films Grown on Low Cost Substrates

We report a systematic investigation of temperature dependent magnetic properties of FePt single and FePt(30)/M/Fe(5) nanocomposite thin films prepared by sputtering technique on low cost substrates at ambient temperature and post annealed at different temperatures. With increasing annealing temperature, L10 ordering, hard magnetic properties and thermal stability of FePt films are improved. The formation of interlayer exchange coupling between hard and soft magnetic layers in FePt/M(Al,Cu,C)/Fe films depends strongly on interlayer materials and interface morphology. A strong interlayer exchange coupling was achieved when the C interlayer thickness was about 0.5 nm, which enhances saturation magnetization largely. Also, the magnetization reversal process changes from incoherent to coherent switching process, which results a single hysteresis loop. High temperature magnetic studies revealed that the effective reduction in the coercivity decreases from 34 Oe/K to 13 Oe/K by the introduction of a thin C(0.5 nm) layer in FePt/C/Fe film. This reveals a promising approach to improve the stability of hard magnetic properties at high temperatures, suitable for high temperature magnetic applications.