HITPERM soft-magnetic underlayers for perpendicular thin film media.

A class of nanocrystalline alloys, HITPERM (Fe, Co)-M-B-Cu (M=Zr,Hf,Nb, etc.) found to exhibit excellent soft-magnetic properties is being studied for use as a soft-magnetic underlayer for perpendicular recording media. Previously, we reported that HITPERM films of ∼100 nm thickness sputtered at room temperature (RT) and at ∼2.3 W/cm[SUP2]power density had exhibited an amorphous microstructure, which had turned mixed nanocrystalline when prepared at ∼250 °C. However, nanoparticles of FeCo have now been crystallized even at RT without the application of heat, by increasing the sputtering power density to ∼4.5 W/cm[SUP2]. This dramatically improved the 4πM[SUBs] while still maintaining a low coercivity. There was a further slight increase in the 4πM[SUBs] at ∼6.8 W/cm[SUP2]. Moreover, these soft-magnetic properties were maintained even when the substrate temperature was subsequently raised to ∼250 °C. Transmission electron microscopy studies showed the presence of relatively small nanocrystals of the ferromagnetic α'-FeCo (or α-FeCo) phase alone, for both sets of films. Previously, we had reported that the CoCrPt magnetic layer grew with a strong (00·2) texture on amorphous HITPERM. We have now seen that with a thin Ti intermediate layer (∼5 nm) the CoCrPt layer maintained a strong (00·2) texture even on the nanocrystalline HITPERM. Thus, due to their particular nanocrystalline nature, these HITPERM films exhibit much better soft-magnetic properties, while still leading to strong (00·2) texture on the CoCrPt magnetic layer. [ABSTRACT FROM AUTHOR]