The effect of surface roughness on magnetoresistance (MR) and magnetic properties of Ta/NiFe films is investigated as a function of surface roughness and NiFe thickness. The surface roughness effects on the MR ratio, Δρ/ρ, of Ta/NiFe films can be separated into two different regimes. In regime I, Δρ/ρ of NiFe films linearly decreases with increasing roughness mostly due to the increase in resistivity of NiFe, while Δρ remains constant. In regime II at increased roughness, domain wall pinning is induced by surface roughness causing a degradation of the uniaxial anisotropy of NiFe and leading to the decrease in Δρ, resulting in the steeper MR ratio decrease. The change in MR properties of NiFe films with varying thicknesses can be correlated with the change in surface resistivity, ρs. Strongly textured NiFe(111) grown onto smooth substrate yields higher anisotropy and lower coercivity than those deposited onto rough substrates over a wide range of NiFe thicknesses.

Strongly textured NiFe(111) underlayers, deposited by dc magnetron sputtering with applied substrate bias, are utilized to grow large, epitaxial grains of FeMn(111). These perfectly oriented (111) NiFe/FeMn bilayers exhibit the highest interfacial exchange anisotropy energy (0.17 erg/cm2), lowest coercivity (∼2 Oe) of the pinned layer, and highest blocking temperature (205 °C) ever reported, to the best of our knowledge. The relationship between the blocking temperature and the x-ray diffraction intensity of FeMn(111) indicates that the exchange interaction across the NiFe and FeMn interface is enhanced by the well-oriented, large, defect-free FeMn(111) crystals.

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A promising soft magnetic under layer (SUL) structure consisting of anti-parallel coupled soft layers (APS) is investigated to improve the performance of high-density perpendicular recording media. CoCrPt-O recording media with average grain diameter 6 nm, coercivity of 5 kOe and nucleation field of 2 kOe is fabricated on both conventional SUL and APS. Wide-area adjacent track erasure (ATE) is observed for conventional SUL, which increases at lower interlayer spacing ( ). APS structure enables the suppression of ATE even up to = 10 nm. Moreover, APS leads to reduced dc erase noise and improved signal to noise ratio particularly for SUL thicknesses 100 nm.Index Terms-Adjacent track erasure, oxide media, perpendicular recording, recording performance, soft magnetic under layer.

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We have successfully demonstrated longitudinal recording at areal density of 130 Gb/in2 at a data rate as high as 170 Mbps (21 MB/s) and at a bit-aspect-ratio (BAR) of 2.9, using merged inductive-write/spin-valve-read heads on low noise thin film disks. The heads were fabricated with the standard photolithography and wafer pole trimming used in our currently available commercial products. The reader is a bottom synthetic spin valve (BSSV) with a 0.09 μm gap, and the writer has a conventionally trimmed pole with 0.09 μm gap. The reader magnetic read width (MRW) was measured at 0.10 μm. At read bias of ∼4 mA we measured reader sensitivity as high as 20 mV/μm. The write head was also optimized for tracks as narrow as 0.14 μm operating at overwrite (OW) of 36 dB and nonlinear transition shift (NLTS) better than −25 dB at 610 kBPI, without precomp. Using conventional media we measured total spectral SNR∼18 dB. The media to electronics noise ratio was 4.8, showing that we are still operating in a media noise limited system. Low-flying air bearing surface (ABS) design and advanced pole tip recession (PTR) control were required to achieve magnetic spacing of about 15 nm.