This thesis is composed of two parts ; the first part concerns the soft magnetic property of CoFe films by adding B, N and B and N together. The second part concerns effect of inserting layers on exchange field and coercivity in CoFeB/IrMn interface.
In the first part, effects of B, and N addition on CoFe films on magnetic properties and thermal stability of the magnetic properties were studied. When B was added, saturation magnetization(Ms) slowly decreased and coercivity(Hc) increased at lower B contents then decreased with increasing B addition. Good soft magnetic property at high B contents is associated with formation of an amorphous film. An amorphous structure was stable only up to 200 ℃ annealing and crystallization occurred at 300 ℃ annealing when Boron content was relatively low(16 chips).
Unlike B addition, Ms dropped rapidly when sputtering partial pressure of N increases. This was more pronounced as the total sputtering pressure increased form 2 mtorr to 9 mtorr. Also, there was some problems with reproducibility. Both B and N were added together, Hc decreased rapidly with increasing N partial pressure without too much reduction of Ms. However, upon annealing at 200 ℃ Ms dropped rapidly accompanied by Hc increase. Therefore, we concluded that CoFeB film is superior soft magnetic film.
In the second part, we have studied effect of thin non magnetic insulated layer such ad Cu, Ag, Ta on exchange field change and coercivity in CoFeB/IrMn exchange bias films. When Ta was inserted, there was no exchange bias field even at 0.6 nm thickness. However, Cu and Ag was inserted there were exchange bias field even at 1.2 nm thickness. The exchange decay suggests that at 0.6 nm thickness of Cu, there are no direct exchange field through pin hole.
Previously ferromagnetic/antiferromagnetic coupling is considered due to direct exchange coupling between spins of ferromagnetic layer atoms and Mn atoms at the interface. However, this experiment shows there is a long range exchange interaction meditated by electrons of the inserted layer and the strength of the long range exchange interaction depends on electronic structure of the inserted layer.
By inserting Cu layer, the coercivity of CoFeB is much reduced and this is due to the reduced exchange bias effect from IrMn antiferromagnetic layer. The reversal of CoFeB becomes more wall motion dominated. In the thin inserted Cu layer in CoFeB/(0.6 nm)Cu/IrMn is stable up to 200 ℃ for annealing and exchange field is increasing and coercivity of CoFeB layer is decreasing . This will serve as a good underlayer in a double layered perpendicular recording media.
