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An anisotropy enhanced dual magnetic layer structure is proposed to improve the recording performance of perpendicular media. The initial layer is made of low noise Co-Cr-Pt-O layer and the top layer is made of higher anisotropy Co-Cr-Pt-B layer. A higher nucleation field than the single layer structures is obtained for the dual magnetic layer media. By optimizing the layer structure and properties, better signal-to-noise and lower adjacent track erasure can be achieved for the dual magnetic layer design over single magnetic layer media.

The correlation between grain morphologies and magnetic properties of CoCrPt/Cr thin films was investigated by varying the sputtering deposition parameters of CoCrPt thin films. Independent of sputtering conditions, the Cr underlayer enhanced Co-grain isolation and limited grain growth in CoCrPt films, resulting in increased coercivity. Cross-sectional transmission electron microscopy indicated a strong separation of the Co grains with increasing argon sputtering pressure, due to the enhanced scattering of argon ions by sputtering particles, and thus the observed higher content of Pt in the deposited films. The Co grains separated by 10–20 A thick non-magnetic boundaries were found to grow on a single larger Cr grain, resulting in reduced exchange coupling and increased coercivity. The application of substrate bias increased the (1010) texture of the Co grains and decreased the grain size of the CoCrPt thin films. In addition, the quality of Co epitaxial growth on the Cr underlayer was enhanced by increasing bias, and the boundary layer between the Cr and CoCrPt films became less distinct as a result of interdiffusion. The magnetic field required to saturate the film increased significantly with increasing substrate bias, possibly due to the induced residual stress in the bias-sputtered films.

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 li...

We have studied thermal stability and recording characteristics of CoCrPtB alloy media with varying c axis anisotropy dispersion, preferred orientation (PO), and in-plane orientation ratio (OR) on both glass and NiP-plated Al substrates. With increasing in-plane c axis orientation and OR, improved recording performances such as lower pulsewidth, lower media transition noise, and lower dc noise are achieved. Thermal decay rate is primarily determined by Co anisotropy dispersion and in-plane OR for the same coercivity media. Media having a large out-of-plane c axis component exhibit a wide switching field distribution and have a high signal decay rate. The PW/sub 50/ and dc noise of media with out-of-plane Co grains are very sensitive to changes in write field. On the other hand, highly oriented media having high OR are less sensitive to head writability variations and offer good thermal stability with excellent recording performance.

Summary form only given. Perpendicular magnetic recording (PMR) media has been considered as a promising candidate in order to achieve over 100 Gbir/in2 recording density. However, thermal stability at low recording densities has been a concern especially for low-noise PMR media. Achieving high perpendicular HC and unity squareness (SQ=Mr/Ms) is necessary to improve thermal stability and has been proposed by using either high substrate temperature or post annealing in CoCr based alloy. However, the influence of high heating on recording performance deserves further investigation. In this work, we studied on the seedlayer and heating effects on the crystallographic, magnetic and recording properties of CoCr18Pt16B4 granular PMR media. The CoCrPtB films were sputtered on preheated glass substrates with a Ru underlayer (UL) or a Ta/Ru UL on top of a 300-nm-thick NiFe17Mo4 soft magnetic underlayer. We report that Ta/Ru UL developed in this study greatly enhances Ru(0002)/Co(0002) crystallography, HC, SQ and thermal stability without degrading media signal-to-noise ratio (So/Nm).

Magnetoresistance (MR) and Planar Hall effect (PHE) of Ta 50 A/NiFe 60 A/Co 90 Fe 10 10 A/Cu 20 A/Co 90 Fe 10 10 A/NiFe 23 /AFeMn 100 A/Ta 50 A spin valve were measured with the magnetic field applied in the plane of the sample. A single batch thin film was etched parallel and perpendicular to the easy direction of the pinned layer. When the field and current were applied along the easy direction, we observed a clear evidence of before- and after-domain rotation of the free layer, near H =0. Larger after-domain rotation of the free layer effect was observed in the sample etched along the hard axis, because the shape anisotropy tilted bias field made the hysteresis of the pinned layer have a longer tail beyond H >0.

The interface magnetostriction (MS), /spl lambda//sub i/ of NiFe films (thicknesses:50 to 500 /spl Aring/) encapsulated with Ta and Al/sub 2/O/sub 3/ layers was studied in as-deposited and thermally annealed states. The MS of NiFe films encapsulated with only Ta (or Al/sub 2/O/sub 3/) layers increase (or decrease) rapidly with decreasing NiFe thickness, due to giant positive (or negative) /spl lambda//sub i/. The magnitudes of both positive and negative /spl lambda//sub i/ increase noticeably with processing at elevated temperatures. In structures containing Ta/NiFe and NiFe/Al/sub 2/O/sub 3/ interfaces, the total interfacial MS contribution is greatly reduced due to the opposite signs of /spl lambda//sub i/ at NiFe interfaces, leading to negligible thickness dependence of the effective MS in as-deposited and annealed states. The strong interfacial MS induced anisotropy affects markedly the uniaxial anisotropy of NiFe films for thicknesses below 100 /spl Aring/.

FeMn based spin valves exhibiting high GMR ratio and high exchange bias field were fabricated by improving the interface roughness as well as the crystallographic texture. A highly oriented (111) NiFe free layer deposited with substrate bias promoted strong (111) textures of Cu and FeMn while maintaining sharp interfaces, resulting in a high exchange bias field, a high blocking temperature, and a high GMR ratio. The correlation between the interlayer coupling energy (J/sub free-pinned/) and the interface sharpness was studied as a function of Cu spacer thickness for spin valves with free and pinned NiFe layers deposited under various bias conditions.

Perpendicular magnetic recording (PMR) has been recognized for many years as having the potential to extend recording densities beyond the capabilities of longitudinal recording. This paper discusses the challenges in designing perpendicular thin-film recording media materials.

In this study, the effect of process parameters on magnetic and recording properties of MiniDiscs is reported. Processes have been tailored to optimize the recording performance of MiniDiscs, such as carrier-to-noise ratio (CNR) at low magnetic fields, recording power margin, and recording power threshold. At higher deposition pressures or lower deposition rates of TbFeCoCr, the external bias field sensitivity of the carrier becomes worse but the noise at high bias fields (>200 Oe) decreases, resulting in improved CNR at high bias fields. Disks with TbFeCoCr sputtered at low pressure or high deposition rates produce a high error rate at high recording power (>4.5 mW), due to jitter noise caused by interference of neighboring magnetic domains. The power margin of the disks is strongly affected by the pressure and deposition rate of TbFeCoCr. When the Curie temperature of the TbFeCoCr layer is lowered by 30 °C (alloy change), the power margin decreases significantly and CNR is decreased by ∼2 dB because of ...

Fe/sub x/Ge/sub 100-x/ films with compositions in the range 50/spl les/x/spl les/82 at 300 K were deposited by rf diode, sequential sputtering from elemental targets. All the films were amorphous at 300 K indicating that the Fe concentration in the stable amorphous films was increased by more than 10 at. % over that obtained by vapor deposition. The sequentially sputtered Fe-Ge films exhibited a heteroamorphous morphology with nanoscale features that varied with composition. The variations in the 4/spl pi/M/sub s/ and T/sub c/ for the sputtered Fe rich films, agreed well with data extrapolated from measurements on Ge rich evaporated films. The improvement in the soft magnetic properties produced in these films by rotating magnetic field annealing (RFA) was shown to be correlated with changes in film morphology.

Effect of Co grain morphology on Cr segregation induced magnetic properties was investigated in heat treated CoCrPt/Cr thin films. In this work, interdiffusion and Cr segregation induced Co grain isolation were studied by post-deposition annealing of the CoCrPt films deposited on a Cr underlayer at different sputtering conditions. The films with voided boundaries showed a stronger heating temperature dependence of magnetic properties than the dense films, due to the promoted Cr segregation at the boundaries. TEM observation indicated that Cr was segregated from the Cr underlayer to the void boundaries of the CoCrPt films. The grain morphology of as-deposited films played an important role in Cr segregation during heat treatment, and the intergranular exchange decoupling was enhanced by the diffusion of Cr atoms into the voids isolating the Co grains.

A highly sensitive optical interferometer with in-situ calibration was developed to measure the low-field magnetostriction of magnetic thin films using the cantilever beam technique, The high displacement resolution (0.01 /spl Aring/) of this instrument permits the measurement of magnetostrictions of 10/sup -9/. First measurements on a soft CoFeSiB thin film were made to demonstrate this technique. The magnetostriction measurement resolution of 5/spl times/10 obtained is the lowest yet reported value. The dynamic range of the technique was demonstrated in measurements of a magnetostriction greater than 10/sup -5/.

Amorphous wires and ribbons of composition Co/sub 70.5/Fe/sub 4.5/Si/sub 15/B/sub 10/ have a very small magnetostriction and very low coercivities for wall motion. Their high permeabilities are of considerable technological interest. Thin films of these alloys might be useful for applications, but had not been previously studied. This work studied the structural and magnetic properties of amorphous thin films sputtered from an alloy target with the composition Co/sub 70.5/Fe/sub 4.5/Si/sub 15/B/sub 10/. The results obtained show that the coercivity and in-plane anisotropy of the sputtered films are much larger than those of ribbons and wires. Attempts to reduce these parameters by varying the processing and annealing parameters, substrate material, composition, and film thickness were largely unsuccessful. While these results are not understood, the composite data suggests that the higher values may be due to micro-compositional inhomogeneities resulting from higher effective quench rates of sputtering.

Exchange-shifted hysteresis loops were observed at 300 K in thin amorphous films deposited from a CoFeSiB alloy target by reactive oxygen sputtering. The heterogeneous film morphologies consisted of nanoscale features with thin, apparently oxidized, boundaries, The exchange shift varied with the film thickness, and with the ratio of the oxygen to argon gas flow, The CoFeSiB:O films exhibiting exchange anisotropy had resistivities in the range /spl sim/10/sup 3/ /spl mu//spl Omega//spl middot/cm to /spl sim/10/sup 4/ /spl mu//spl Omega//spl middot/cm. The maximum shift (/spl sim/10 Oe) was observed in films with a resistivity of /spl sim/2500 /spl mu//spl Omega//spl middot/cm. The exchange anisotropy appears to be due to coupling between nanoscale regions with different coercivities.

Multilayered Co–B films with various bilayer periods (BP=TCo+TB, TCo=4×TB) and ratios of bilayer thickness were ion beam mixed with 150 keV 1016 Ar ions/cm2. The morphologies of both the as‐deposited and the ion beam mixed films changed with BP. The ion beam mixed films exhibited amorphous structures, and the morphologies differed as a function of layer thickness in the as‐deposited state. The morphological differences appeared to influence magnetic properties such as in‐plane anisotropy and coercivity. Magnetization measurements revealed that the compositional inhomogeneities resulted in the anomalous extension of ferromagnetic composition range compared to melt‐quenched films.

We investigated the effect of bias sputtering on the oxidation resistance of amorphous Tb32Fe68 compositionally modulated films (CMFs). The columnar morphologies of aged, unbiased films were more diffused than those of as‐deposited films. On the other hand, the morphologies of the −70 V bias sputtered, aged film were as dense and featureless as those of as‐deposited films. The substrate bias also influenced the magnetic and magneto‐optical characteristics of aged films. The Kerr rotation obtained from the film surface was significantly increased by the formation of a transparent, nonmagnetic oxide layer, and by optical interference between this layer and the unoxidized amorphous matrix. The coercivity of the amorphous matrix in unbiased films increased markedly with aging time. These changes are attributed to compositional changes enhanced by the easy diffusion path of oxygen in the columnar void structure. In contrast, the coercivity of −70 V bias sputtered films was unchanged with aging, and exhibited t...

Amorphous Gd17Co83 compositionally modulated films (CMFs) with different bilayer periods were prepared by sequential deposition in a rf diode multitarget sputtering system. Morphological inhomogeneities with variable size, shape, and uniformity on the scale of 20–100 A were produced by variations in deposition parameters including substrate bias. Data from small‐angle electron scattering and Fourier digital image processing of TEM micrographs revealed that the morphological inhomogeneities were due to compositional fluctuations. The −65 V bias sputtered films (bilayer period

The effects of grain morphology and crystallography on the magnetic properties of CoCrPt/Cr thin films were investigated as a function of sputtering parameters of CoCrPt thin films. Cross sectional TEM exhibited strong separation of Co grains with increasing argon sputtering pressure, resulting in reduced exchange coupling and increased coercivity. Most Co grains sputtered at high pressure were separated by 10 to 20 Å thick boundaries, possibly due to the enhanced scattering of argon ions by sputtering particles and thus the observed higher content of Pt in the deposited films. The application of substrate bias greatly decreased the Co grain separation and the nonmagnetic grain boundary disappeared by -200 V bias sputtering, resulting in increased exchange coupling. The bias sputtered CoCrPt thin films decreased their grain size and increased epitaxial growth on Cr layer and also (1010) texture. The magnetic field required to saturate the film increased significantly with increasing substrate bias, possibly due to the induced residual stress in the bias sputtered films.

Nanocomposite thin films with coexisting magnetic metal and magnetic nonmetal amorphous phases were synthesized by reactively sputtering CoFeSiB:O thin films with a large silicon (15 at.%), and varying oxygen concentrations. The microstructure, magnetization, and hysteresis loops were measured for films with resistivities near the metal–nonmetal transition. These data revealed that, below the metal–nonmetal transition, conductive transport was along the soft magnetic, metallic backbone of the percolation network; the nonmetal phase was a discontinuous, randomly distributed, hard magnetic oxide. The metallic resistivity and exchange anisotropy were both maximized in a nanocomposite with a resistivity at the metal–nonmetal transition.

Artificially layered structures have attracted attention because of their unique structural and magnetic characteristics. It has been reported that in these structures the anisotropic distribution of atomic pairs can play an important role in determining their magnetic anisotropy.1 Our previous work showed that the application of substrate bias in a rf diode sputtering system was effective in producing dense and stable amorphous compositionally modulated films (CMFs).2 In this work, we studied the interrelationships of the structural and magnetic properties of amorphous Tb‐Fe CMFs deposited under various substrate bias conditions (0, −70, −90 V) in a multitarget rf diode sputtering system. Although considerable research has been conducted on the effect of ion bombardment during deposition on the film structure, it has been difficult to independently control the film structure and the composition in such experiments because of the preferential backsputtering of atoms.Accordingly, in this research we system...

We report on a study of the effect of oxygen on the chemical and structural stability of compositionally modulated Gd‐Co multilayer films. Films with bilayer periods (BP) from 10 to 300 A were prepared by alternate deposition in a multitarget RF diode sputtering system. Oxygen incorporation in the films was controlled during deposition by the application of rf substrate bias, and after deposition by annealing. Oxygen preferentially accumulated in the Gd layer and blocked its diffusion. Co columnar grain growth in samples with large BP appears to be associated with the asymmetric diffusion between the Gd and Co layers. TEM of samples with small BP showed a void network structure in the samples sputtered with 0 V substrate bias, but showed a phase separated amorphous structure in the samples sputtered with 65 V substrate bias. Annealing suppressed the growth of crystalline Gd and Co in samples with oxygen but enhanced the nucleation of GdCo2. A strong growth of Co and Gd grains occurred in annealed samples with low oxygen content but GdCo2 was not observed. Cross‐section TEM showed that the growth of these grains was limited by the layer boundaries.

Ion beam mixing (with 150 keV 1016 Ar ions/cm2) of multilayered Co-B films with various bilayer periods (BP = TCo + TB, TCo = 4 × TB), and layer thickness ratios, was studied to determine its utility, compared to sputtering, in producing morphological changes in amorphous thin films. All the ion beam mixed films were amorphous, but the morphologies of both the as-deposited and the ion beam mixed films varied with the BP. The in-plane, easy axis anisotropies of the films with the largest BP were obliterated by mixing, although their hard axis coercivities were unchanged. The anisotropy of the films with smaller BPs was increased by mixing. The results indicate that ion beam mixing is a potentially useful method of improving the properties of soft magnetic thin films.

Amorphous Tb/sub 32/Fe/sub 68/ compositionally modulated films were prepared in a multitarget RF diode sputtering system. Independent control of the RF voltage ratios of both the Tb and the Fe target allowed the composition of the film to be held constant as the substrate bias was changed. Cross-sectional transmission electron microscopy showed that small-scale atomic clusters were aligned in layers. Bias sputtering appeared to enhance the magnetic and magnetooptical properties and modified the film structure from a columnar void to a dense, featureless morphology. The surface magnetic properties and magnetooptical responses of the unbiased films were dominated by selective oxidation of Tb. Films deposited with 70-V bias, however, exhibited stable magnetic properties and uniform magnetooptical responses throughout the film thickness. >