First-Order Reversal Curve Investigations on the Effects of Ion Implantation in Magnetic Media

Ion implantation of different ion species of varying mass on magnetic recording media was investigated. Except for helium (4He⁺) and cobalt (59Co⁺) ions, all the other ions showed reduction in saturation magnetization (M_s). In fact, M_s was reduced to ~ 0 emu/cc at a fluence of 2 × 10¹⁶ and 5 × 10¹⁶ ions/cm² for antimony (121Sb⁺) and argon (40Ar⁺ ) ions, respectively. First-order reversal curves (FORC) showed a reduction in the switching field and distribution as the fluence of the implanted species increased. In addition, the magnetostatic interactions which were present in the media were found to be overwhelmed by an increase in exchange interaction as fluence increased. It was noticed that the heavier the implanted ion, the lower was the lateral range and straggle. A negative correlation was also observed between the straggle of the implanted species and the increased exchange interaction. This observation is expected to play a very crucial role in high-density patterned media fabrication.