Focused-ion-beam processing of magnetic materials for magnetic recording heads

The objective of this work is to develop fundamental knowledge about focused-ion-beam (FIB) processing of magnetic materials for recording heads. To fulfill this goal, the effects of FIB processing on magnetic materials and recording heads, which may be concerns for the use of FIB in recording head pole trimming, were examined. Local magnetic modification induced by FIB processing of magnetic thin films was investigated using magneto-optic Kerr effects. Quantitative magnetic characterization of FIB-etched magnetic thin films was carried out. Also, microstructural and chemical modification due to FIB irradiation was characterized. FIB-induced grain growth was characterized and it was found that FIB processing causes considerable grain growth in magnetic thin films. Experimental results suggested the FIB-induced grain growth is driven by momentum transfer rather than a thermal process due to local heating. FIB-induced Ga implantation was characterized using energy dispersive x-ray (EDX) and Auger electron spectroscopy (AES). AES was used to obtain the Ga implantation depth in two different directions: the depth direction and lateral direction. AES depth profiles showed that the Ga implantation depth is ∼10 nm in the lateral direction and ∼100 nm in the depth direction. Knowledge on these implantation depths is relevant to the formation of pole geometries with sub-micrometer or nanometer scale. Finally, effects of FIB irradiation on perpendicular writer performance (PW₅₀ and SNR) were examined on a spin-stand. At a dose of 300 pC/μm2, PW₅₀ showed an increase by 33 nm (>30%) and SNR showed a decrease by 5 dB (>25%). Performance degradation with doses <25 pC/μm2 was attributed exclusively to the formation of magnetic dead layer. According to write spacing loss analyses, the thickness of magnetic dead layer was 1 nm per 10 pC/μm 2.