Co, Ni, Mn, Cr and Cu substituted magnetites were prepared by the hydrothermal method at 300°C, with concentrations x ranging from 8.2 to 12.5%. Transmission electron microscopy determined the average particle diameter <Φ> to be in the hundred of nm range and the morphological modifications induced by the various substitutions employed. Hysteresis loop measurements were performed to determine the coercive field Hc and saturation magnetic moment ms. While Hc decreased with increasing <Φ>, the particle shape was found to play an important role in explaining the dependence of ms on <Φ>. Transmission Mössbauer spectroscopy was used to determine the site preference of the substitutions and their effect on the hyperfine magnetic fields. The room temperature Mossbauer spectra were analyzed assuming a random distribution of substitutents using the binomial distribution from the ionic crystal point of view. Superparamagnetic particles were observed at room temperature in the case of Cu and Cr substituted magnetites.

During the wafer manufacturing process of magnetoresistive (MR) heads which are widely used in Hard Disk Drives, the metal leads are deposited on both sides of the MR sensing element through the photoresist masks. Due to the shadowing effect of the photoresist, there may be some contamination at joint interfacial region even after ion etching. This introduces additional contact resistance and causes some region of the sensing element to be unpinned. As the geometry of the sensor element decreases, and the contamination, located in regions of few thousands of angstroms, is becoming more severe for MR head than ever. In this paper, we developed a systematic method to evaluate the contact resistance between the two metal layers. A comparison was made between the magnetic read width and the physical width. Finally TEM analysis successfully revealed the interfacial junction contamination.

A series of Co-rich CoAg heterogeneous thin films, with Co concentrations greater than 65 % volume fraction and film thickness in the range 5 nm - 50 nm, was prepared by dc magnetron sputtering. Annealing in high vacuum (P < 3x10-7 Torr) above 400°C was necessary to promote phase separation between the two elements. Maximum room temperature coercivities, Hc ∼ 900 Oe, were obtained at a thickness of 20 nm for CoAg 70:30 vol % films. These coercivities are almost two orders of magnitude larger than the values observed in as-deposited films. The concentration of maximum coercivity, that is usually associated to the threshold for magnetic percolation, is much higher than the 40-50 vol % commonly observed in bulk granular materials. The shift in the magnetic percolation limit was related to the reduced dimensionality of the very thin films. Coercivity was found to vary both with film composition and with thickness. Delta M curves and time decay (magnetic viscosity) measurements were done to determine the interparticle interactions and the activation volumes. A maximum in the remanent coercivity (coincident with the maximum in Hc) was found for a film thickness φ ∼ 15-20 nm in all the alloys. At this same thickness a negative minimum in the interparticle interaction parameter α (indicating that the particle interactions favor the demagnetized state) was observed. The absolute value of a increases for larger Co concentrations. The irreversible susceptibility is an increasing function of film thickness and the magnetic viscosity has a minimum for φ ∼ 15-20 nm. The activation volume also increases with thickness, changing from (15 nm)3 to (40 nm)3 for the more diluted alloys, values similar to the average particle size determined by transmission electron microscopy.

Experimental measurements of the aftereffect along a magnetization reversal curve are compared with the predictions of a Preisach-Arrhenius model for a high density particulate recording medium. The Preisach parameters are determined from the measurement of the major hysteresis loop and the remanence loop. The Arrhenius parameters were determined from a single aftereffect curve. It was then found that the model gives good qualitative agreement with both the initial slope and, for the case in which the aftereffect is not monotonic, the peak value of the aftereffect.

The behavior of the compensation temperature of a mixed Ising ferrimagnetic system on a square lattice in which the two interpenetrating square sublattices have spins σ (±1/2) and spins S (±1,0) has been studied with Monte Carlo methods. Our model includes nearest and next-nearest neighbor interactions, a crystal field and an external magnetic field. This model is relevant for understanding bimetallic molecular ferrimagnetic materials. We found that there is a narrow range of parameters of the Hamiltonian for which the model has compensation temperatures and that the compensation point exists only for small values of the external field.

Amorphous hard carbon films deposited by filtered cathodic arc deposition exhibit very high hardness and elastic modulus, high mass density, low coefficient of friction, and the films are very smooth. All these properties are beneficial to applications of these films for the head/disk interface tribology. The properties of cathodic arc deposited amorphous carbon films are summarized, and they are compared to sputter deposited, hydrogenated (CHx), and nitrogenated (CNx) carbon films which are the present choice for hard disk and slider coatings. New developments in cathodic arc coaters are discussed which are of interest to the disk drive industry. Experiments on the nanotribology, mass density and hardness, corrosion behavior, and tribochemical behavior of cathodic arc films are reported. A number of applications of cathodic arc deposited films to hard disk and slider coatings are described. It is shown that their tribological performance is considerably better compared to CHx and CNx films.

Diamond like carbon (DLC) films are deposited on thin film heads in the magnetic recording industry to reduce friction and “stiction” and to provide a durable, abrasion resistant coating. The films are a mixture of graphitic phases with sp2 bonding and diamond phases with sp3 bonding. The present work provides the results of thin film stress measurements and Raman tests performed on 10 rim DLC films deposited on 75 mm silicon test wafers using standard optical lever techniques. Stress is measured after deposition and in-situ during thermal cycling. Isothermal relaxation data is also obtained. Raman is performed before and after annealing.

The deposited stress of 10 nrm films was over 2000 MPa. The stress relaxed entirely to zero during thermal cycling to 500°C. Isothermal relaxation at 300°C also resulted in complete relaxation of an initial 1500 MPa stress to zero in less than 24 hours. The Raman data is consistent with prior results in the literature. The position of the G band shifts from 1513 to 1581 cm-1 during annealing, and the intensity ratio of the D band to the G band rises from 0.201 to 0.814 during annealing.

The decrease of the film stress to zero during thermal processing implies that the entire thickness of the film is undergoing a structural change while the stress relaxation data implies that the stress is relaxing by a fast diffusive process. The Raman data implies that the film is becoming more graphitic and the crystallites are growing in number and size during thermal processing. We suggest that the structure of the extremely thin carbon film is modified by a surface diffusion mechanism.

In this investigation, the wear durability of existing and candidate protective overcoats and substrates was examined. Specifically, 5 nm thick diamond-like carbon (DLC) and nitrogenated diamond-like carbon (N-DLC) overcoats were deposited by sputtering onto glass, glass-ceramic, and NiP/AlMg substrates. The magnetic medium was a 15 nm thick layer of CoCrPt deposited on a 50 nm thick underlayer of CrV. The wear resistance of the hard disks was determined by a recently developed depth sensing reciprocating scratch test using the Nano Indenter© II. During the scratch tests, a constant normal load of 30 jtN was maintained at an indenter velocity of 2μm/sec. It was found the N-DLC/CoCrPt/CrV/glass disk exhibited the most wear resistance and least amount of plastic deformation after the last wear event. Conversely, the NDLC/CoCrPt/CrV/NiP/AiMg disk displayed the least wear resistance even though the magnitude of the elastic recovery was the greatest. This amount of recovery was influenced by the high elastic modulus of the NiP/AIMg substrate. Consequently, the scratch test failed to isolate the intrinsic properties of the overcoat, however it provided a very powerful means of quantitatively assessing the overall response of the whole magnetic disk. This is more relevant since it simulates the response the disks see in performance. In addition, a discrete amount of nitrogen up to 14 atomic % incorporated into the amorphous network resulted in an increase in overcoat durability compared to the DLC overcoat. This was attributed to an increase in the XPS determined number of N-sp3 C bonded sites in a predominantly N-sp2 C bonded matrix. However, with increasing nitrogen concentrations ≥18%, the film structure was weakened due to the micro-Raman spectroscopy determined formation of terminated sites in the amorphous carbon network since nitrogen failed to connect the sp2 domains within the network.

This paper presents experimental and analytical studies of AFM nanoindentation as a method to determine microhardness of hard thin films. Indentations are performed on Au, Si, and DLC using triangular pyramidal diamond probes to determine microhardness. We examined the effects of indentation force and three different methods to measure the indentation area (direct area measurement for a triangular indentation, size analysis of an inverted AFM image of the indentation, and prediction of area from indentation depth based on a tip shape function). The responses are indentation depth, projection area, and microhardness. Relationship of responses with indentation force is examined. At a low depth range, microhardness based on pyramidal shape function is erroneously higher than the other two methods. However, all three methods generally agree with each other when indentation force exceeds 16μN. Size analysis of inverted images gives more consistent microhardness with the least variability over the whole force (4∼30μN) or depth (0.5∼70 nm) range. Tip shape models are developed to predict microhardness. The ellipsoidal tip model is a good approximation at low depth ranges, while the pyramidal model works better for deeper indentations. The force vs area curves are also significantly nonlinear which can distort the hardness measurements.

Surface energies of molecularly-thin, perfluoropolyether (PFPE)-lubricated, amorphous carbon surfaces are presented as a function of the applied PFPE structure and thickness. A framework is developed to aid in the interpretation of the surface energy data. Information regarding the structure of these PFPE films adsorbed on CHx at the monolayer thickness levels is elucidated. Evidence for ordering in these polymer films is presented and interpreted to result from a combination of both, lateral cohesive interactions within the plane of the monolayer, and adhesive interactions between the PFPE monolayer and the underlying substrate.

X-ray Photo Emission Electron Microscopy (X-PEEM) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy were applied to study the properties of amorphous hard carbon overcoats on disks and sliders, and the properties of the lubricant. The modification of lubricants after performing thermal desorption studies was measured by NEXAFS, and the results are compared to thermal desorption data. The study of lubricant degradation in wear tracks is described. Sliders were investigated before and after wear test, and the modification of the slider coating as well as the transfer of lubricant to the slider was studied. The studies show that the lubricant is altered chemically during the wear. Fluorine is removed and carboxyl groups are formed.

The mechanisms and effectiveness of corrosion protection provided by thin ion-beam carbon coatings on Cu, Fe, Mn and Co are discussed. A thin (# 10 Å) layer of protective carbon is produced on metal surfaces by ion-beam dissociation of adventitious or intentional hydrocarbon adsorbates. Below 200°C, oxidation is strongly inhibited, as is corrosion in a humid, sulphurous ambient. Above 200°C, the carbon layer may itself be destroyed by oxidation, due to catalytic action of the metal surface. Thicker PVD carbon (up to 60 Å) was not an effective corrosion barrier, even after ion irradiation. A technique for producing high integrity ion-beam carbon layers of high stability and durability is discussed.

Laser zone texturing of nickel-plated, aluminum based magnetic media has become a preferred method of providing a precisely controlled head landing zone. The Nd:YAG lasers used for this process are not suitable for directly texturing glass substrates. A novel method has been developed which allows the use of the existing Nd:YAG laser systems to zone texture glass based magnetic media.

An amorphous sputtered film of a non-magnetic Ni alloy provides a texturing layer which absorbs the laser pulse and controllably forms regular, small protrusions. Optimization of the alloy composition results in small cone-shaped bumps. Laser power sensitivity exhibits a region of invariance for a range of film thickness. This behavior provides a wide margin for manufacture by reducing the effect of thickness variation on laser bump height.

Disks fabricated using this form of laser zone texture exhibit excellent tribology performance. TEM images show the Ni alloy to be amorphous and featureless. The sputtered film does not influence the properties of the subsequently sputter deposited isotropic magnetic films.

We report infrared absorption measurements that provide evidence for the presence of boron carbide icosahedra in amorphous hydrogenated boron carbide thin films. The infrared absorption spectra is dominated by an intense line at 1280 cm-1 with a FWHM of ≃320 cm-1. Similar lines have been previously reported in polycrystalline boron carbide, where boron carbide icosahedra make up the unit cell. In both systems, the linewidth narrows and the peak position shifts to higher energy with increasing carbon concentrations. From annealing studies of amorphous hydrogenated boron carbide, hydrogen plays a very small role in the 1280 cm-1 line. Finally, the integrated intensity of the 1280 cm-1 line is a sublinear function of the boron concentration, providing further evidence that the carbon concentration in these icosahedra increases as the carbon concentration of the film increases.

High density, metal particle recording media consists of micron-sized iron particles in a polyurethane based polymer binder. In order to improve the corrosion resistance of the particles, two new amine-quinone (AQ) polymers, AQPU15 and AQPU100, have been investigated. Electrochemical impedance spectroscopy (EIS) was used to evaluate the corrosion behavior of iron substrates coated with two different thicknesses of each polymer. Results showed that the AQ polymers provide better protection compared with commercial polyurethane. The nature of the interaction at the polymer/metal interface has been investigated by FTIR-RA and XPS, which indicate that bonding probably occurs through the n system of the AQ functional group and the nitrogen of the soft segment, and through the quinone carbonyl functional group.

The deposition technologies of rare-earth substituted yttrium iron garnet (RE:YIG) thin films with a large Faraday rotation and their applications are briefly overviewed. Highly cerium substituted YIG films were successfully deposited on (111) GGG, (211) GGG, (100) MgO, and MgO buffered GaAs and InP substrates by single-liquid-source metalorganic chemical vapor deposition. Ce-YIG thin films can be epitaxially grown on lattice matched GGG substrates at a temperature as low as 600°C. They have excellent optical and magnetic properties along with high Faraday rotations. The films deposited on single crystal (100) MgO substrates are polycrystalline and have good magnetic properties. Sputter deposited MgO buffer layer was demonstrated for preventing the decomposition and chemical reaction of GaAs and LnP substrates resulting in successful deposition of YIG films on GaAs and InP substrates at a substrate temperature of 550°C. The films grown on MgO buffered GaAs substrates possessed good magnetic properties.

Garnet films of composition (Lu,Bi)3(Fe,Ga,Al)5O12 and (Tm,Bi)3(Fe,Ga)5O12 are grown by liquid-phase epitaxy on [111]-oriented substrates of gadolinium gallium garnet. Ferrimagnetic films with positive or negative Faraday-rotation as well as paramagnetic films with negligible Faraday-rotation are produced by variations of the rare earth ion substitutions. The temperature dependence of Faraday-rotation is fitted with a molecular field model. Optical rib waveguides in single and double layer garnet films with different Faraday-rotations are realized. The nonreciprocal phase shift of the TM0-Mode is studied both theoretically and experimentally at a wavelength of 1.3 μm. Results show that the maximum nonreciprocal effect at room temperature of double layer films with opposite Faraday-rotation is 1.6 times as large as that of comparable single layer waveguides. But, because of the large temperature dependence of the Faraday-rotation of the positive rotating films, these waveguides show a large temperature dependence of the nonreciprocal phase shift. This problem can be avoided if the positive rotating layer is replaced by a paramagnetic layer. Agreement between calculations and measurements is excellent.

A novel configuration of an integrated optical isolator employing a nonreciprocal phase shift is proposed. The isolator is equipped with a cladding layer of magnetic garnets by means of wafer direct bonding technique. This device has a semiconductor guiding layer, so high compatibility in integrating with other semiconductor optical devices is expected.

The epitaxial separation of single-crystal magnetic and ferroelectric oxide films is presented. Ion implantation is used to create a buried damage layer beneath the surface. The high etch-selectivity of this sacrificial layer makes it possible to detach high quality single-crystal films from bulk samples. Magnetic and electrical properties of the films are discussed.

This work aims to equip integrated optical circuits with important magneto-optical devices, such as isolators, that are currently available only as discrete components. Reactive rf sputtering was used to grow cerium-doped yttrium iron garnet films onto a variety of substrates, including SiO2-buffered Si, fused Si02 and MgO. MgO was used because it has proven to be a good buffer material for semiconducting substrates. Ce-doping was not effective via reactive sputtering due to a scale which formed on the Ce metal that prevented sufficient contact with the rf target. The films were amorphous as deposited. Stoichiometric Y3Fe5O12 films yielded smooth, polycrystalline garnet films upon annealing. A study of the effect of fluctuations in the Y:Fe ratio revealed that oxygen content is important for the prevention of secondary phases. Therefore, a high oxygen content should be used in the sputtering gas and subsequent annealing should be performed in oxygen.