Metal Evaporated Research Articles

Bidirectional recording performance of a perpendicular evaporated Co–CoO tape

It is the first report on the recording performance of a perpendicular metal evaporated (ME) tape measured with a giant magnetoresistive head. To solve the application difficulty of oblique evaporated tape media to linear scan tape systems, a perpendicular evaporated Co–CoO tape was proposed instead. The prepared sample showed perpendicular anisotropy with coercivity of 107.3 kA/m, M r t of 3.9 mA and squareness of 0.25. Identical recording characteristics were obtained for both head-media moving directions, which enables the application of perpendicular evaporated Co–CoO tape to linear scan tape systems. The better carrier-to-noise ratio was also confirmed by comparison with a current advanced product of metal particulate tape, which can realize the higher recording density of linear scan tape systems using ME tape.

Analysis of waveform from perpendicular magnetic printed media

Edge printing is one of the perpendicular magnetic printing methods for writing servo signals with high speed, high accuracy and low cost. Sub-peaks of waveform from edge printed media are concerned as the sub-peaks can cause errors during the read-back process. In this study, in order to reduce sub-peaks, the influence of printing field, bit length and patterned magnetic layer thickness of master medium on sub-peaks is investigated by using a metal-evaporated (ME) tape as a slave medium. The results show that sub-peak to main peak ratio decreases with stronger printing field, smaller bit length and thicker patterned magnetic layer of master media.

蒸着テープを用いた垂直磁気転写解析

The duplication characteristics of perpendicular magnetic media were analyzed by using metal evaporated (ME) tape as a slave medium. In the case of bit printing (BP), the best duplication characteristic was obtained at a duplication field of 4 kOe, about 2 times higher than the coercivity of the ME tape. On the other hand, in the case of edge printing (EP), duplication characteristics were saturated when the duplication field was more than 3kOe. When the duplication field was strengthened, in the case of BP, the peak position shifted towards the outside of the magnetic layer of the master, whereas, in EP, the peak position shifted towards the center of the magnetic layer. The calculated MFM output waveform obtained by using computer simulation almost coincided with the experimental result, and the cause of the sub-peak could thus be explained. It was concluded that EP has better duplication characteristics than BP.

Nanoscale deformation and cracking studies of advanced metal evaporated magnetic tapes using atomic force microscopy and digital image correlation techniques

A custom designed microtensile tester was integrated with an atomic force microscopy (AFM) to perform in situ tensile tests on two advanced metal evaporated (ME) magnetic tapes – ME/polyethylene terephthalate (PET) (with PET as a substrate) and ME/polyethylene naphthalate (PEN) (with PEN as a substrate) where the tape surfaces were imaged simultaneously by AFM during tensile loading. The digital image correlation technique was used to process the AFM images and quantitatively measure local, nanoscale deformation for both front coat and back coat of the ME tapes subjected to uniaxial tensile loading. The surface morphology change, strain distribution evolution and crack initiation and propagation during tensile loading are discussed with the structures and mechanical properties of the ME tapes.

Viscoelastic analysis applied to the determination of long-term creep behavior for magnetic tape materials

Creep-compliance experiments were performed for three representative magnetic tapes. Two of these tapes used a magnetic particle (MP) coating, and one used a metal-evaporated (ME) coating. The MP tapes used the following polyester substrates: semitensilized poly(ethylene naphthalate) (PEN) and supertensilized poly(ethylene terephthalate). The ME tape used an aromatic poly(amide) or aramid substrate. Time–temperature superposition was used to make creep-compliance predictions at 30 and 50°C reference temperatures. Comparisons were made with dimensional stability requirements based on position error signal (PES) specifications for magnetic tape drives along with in-cartridge creep specifications based on PES measurements. Circumferential and lateral creep strains were determined that account for storage of the tapes in a reel, and creep strains were predicted for future tapes with thinner, lower compliance coatings. A rule of mixtures method was also used to extract compliance information for individual layers of MP-PEN tapes, and stress profiles through the thickness of the tapes were determined. Additional measurements and analyses were performed to determine the creep recovery and shrinkage characteristics for the magnetic tapes. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1106–1128, 2006

Improving the corrosion resistance of metal-evaporated tape using dicarboxy acid as a lubricant

To improve the corrosion resistance and frictional durability of ultra-thin metal-evaporated (ME) tape, we have developed a new lubricant with two carboxyl groups that can improve corrosion resistance and frictional durability. The storage life of the ultra-thin ME tape with the new lubricant was evaluated using the Battelle Class II test and estimated to be more than 50 years.

Durability studies of metal evaporated tapes in a linear tape drive: Role of head contour and tape tension

Magnetic performance of metal evaporated (ME) tape makes it a prominent storage media candidate for future data recording systems. However, the durability of ME tapes, limited by a number of tribological issues, is a major concern. A preliminary investigation on durability of ME tapes in a linear tape drive has been carried out. The effect of head contour and tape tension on the durability of the head-tape interface has been studied. An optical microscopy based technique has been used to measure the quality of factory-slit tape edges and after use in a liner tape drive. Debris distribution over the head surface at the end of the testing has been monitored. The ME tapes are found to be sensitive to both head contour and tape tension. Some desirable attributes of ME tapes required to improve durability are discussed.

Spin-Valve Head With Corrosion Resistance for Tape Recording System

This paper reports on a corrosion-resistant spin-valve head (Ta/NiFe/CoNiFe/CuAu/CoNiFe/PtMn/Ta) for a tape recording system. The spin-valve film has a +0.4 V higher electrochemical potential than the conventional spin-valve film (Ta/NiFe/CoFe/Cu/CoFe/PtMn/Ta). The spin-valve head with CoNiFe magnetic layer and CuAu spacer exhibits good corrosion resistance. An investigation of the recording characteristics of the corrosion-resistant spin-valve head with metal evaporated (ME) tapes showed that: 1) the spin-valve head had about 64% of the output voltage of an isolated pulse of the conventional spin-valve head; 2) the carrier-to-media noise (C/N/sub media/) ratio at a wavelength of 0.4 /spl mu/m of the spin-valve head is the same as that of the conventional spin-valve head; and 3) the C/N/sub media/ ratio of thin ME tape with magnetic layer 33 nm thick was maximized at around M/sub r/t=10 mA, where M/sub r/ is the remanent magnetization and t is the magnetic layer thickness. These results indicate that the corrosion-resistant spin-valve head (Ta/NiFe/CoNiFe/CuAu/CoNiFe/PtMn/Ta) for a tape recording system provides high recording density.

A surface topography-independent friction measurement technique using torsionalresonance mode in an AFM

The recently introduced torsional resonance mode (TR mode) technique has been appliedfor friction force measurements at the micro/nanoscale. In this technique, an atomic forcemicroscope (AFM) with a vibrating cantilever tip in torsional mode is used, andthe contact torsional vibration amplitude of the tip motion (TR amplitude) ismonitored at a contact resonance frequency under constant normal load. In thispaper, the TR mode friction force images are compared to the friction force imagesacquired by conventional contact mode friction force microscopy on three samples:a self-assembled monolayer (SAM) with two phase structure, a silicon ruler, and a metalevaporated (ME) tape. The results from those samples show that the TR mode frictionforce images are much less affected by the surface topography and are almostindependent of the scanning direction of the tip, whereas this is not the case forthe contact mode friction force measurements. Mechanisms responsible for theseobservations are also discussed in the paper. In order to predict coefficient of frictionas a function of the change in the TR amplitude, an energy balance model isproposed.

Mechanical, hygroscopic, and thermal properties of metal particle and metal evaporated tapes and their individual layers

AbstractMechanical and thermal properties of magnetic tapes and their individual layers strongly affect the tribology of magnetic head–tape interface and reliability of tape drives. Dynamic mechanical analysis, longitudinal creep, lateral creep, Poisson's ratio, the coefficient of hygroscopic expansion (CHE), and the coefficient of thermal expansion (CTE) tests were performed on magnetic tapes, tapes with front coat or back coat removed, substrates (with front and back coats removed), and never‐coated virgin films of the substrates. Storage modulus and loss tangent values were obtained at a frequency range from 0.016 to 28 Hz, and at a temperature range from −50 to 150 or 210°C. Longitudinal creep tests were performed at 25°C/50% RH, 40°C/25% RH, and 55°C/10% RH for 50 h. The Poisson's ratio and lateral creep were measured at 25°C/50% RH. CHE was measured at 25°C/15–80% RH. CTE values of various samples were measured at a temperature range from 30 to 70°C. The tapes used in this research included two magnetic particle (MP) tapes and two metal evaporated (ME) tapes that were based on poly(ethylene terephthalate) and poly(ethylene naphthalate) substrates. The master curves of storage modulus and creep compliance for these samples were generated for a frequency range from 10−20 to 1015 Hz. The effect of tape manufacturing process on the various mechanical properties of substrates was analyzed by comparing the data for the substrates (with front and back coats removed) and the never‐coated virgin films. A model based on the rule of mixtures was developed to determine the storage modulus, complex modulus, creep compliance, and CTE for the front coat and back coat of MP and ME tapes. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1319–1345, 2004

Analysis of side writing asymmetry

The side writing asymmetry of a recording head was investigated using an overwrite configuration that enhances the edge effects. The track profiles of the overwrite patterns were measured for analyzing the side writing performance of the head. Magnetic force microscope (MFM) images of the overwrite patterns were studied using fast Fourier transforms (FFT), and they confirmed the profiling results. We measured weak edge effects at good pole alignment. The experiments were performed with metal evaporated (ME) and metal particle (MP) tapes having magnetic layers between 50 and 300 nm.

The digital-recording performance of obliquely oriented metal-evaporated tape in the reverse direction

We have investigated the signal-to-noise ratio (SNR) and the nonlinear transition shift (NLTS) properties of recording in both the forward and the reverse directions by using obliquely oriented metal-evaporated (ME) tape. The pulse width at 50% threshold of the reverse direction is 28% wider than that of the forward direction, but the SNR after equalization is almost the same by reducing linear recording density by 14% from that of the forward direction. It is possible, therefore, to use the high-density read/write performance of obliquely oriented ME tape in a linear tape system, which would yield a less-than 7% loss of total recording capacity.

Dynamic mechanical and thermal analyses of magnetic particle and metal evaporated tapes and their individual layers

AbstractThe mechanical and thermal properties of magnetic tapes and their individual layers strongly affect the tribology of the magnetic head–tape interface. Dynamic mechanical analysis and thermomechanical analysis tests were performed on magnetic tapes, tapes with front coat or back coat removed, substrates (with front and back coats removed), and never‐coated virgin films of the substrates. Storage modulus and loss tangent were obtained at a frequency range from 0.016 to 28 Hz, and at a temperature range from −50 to 150 or 210°C. Coefficients of thermal expansion (CTE) of various samples were measured at a temperature range from 30 to 70°C. The tapes used in this research include two magnetic particle (MP) tapes and two metal evaporated (ME) tapes based on poly(ethylene terephthalate) and poly(ethylene naphthalate) substrates. The master curves of storage modulus for these samples were generated for a frequency range from 10−20 to 1015 Hz. The effect of the tape manufacturing process on the dynamic mechanical properties of substrates was analyzed by comparing the data for the substrates (with front and back coats removed) and the never‐coated virgin films. A model based on the rule of mixtures was developed to determine the storage modulus, complex modulus, and CTE for the front coat and back coat of MP and ME tapes. To validate the procedure, data for these individual layers were then used to calculate the corresponding properties of the finished tape. The predicted results were compared with the experimental measurements. The data obtained in the study are also discussed in light of previously published lateral contraction, Poisson's ratio, CTE, and CHE (coefficient of hygroscopic expansion) data. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 548–567, 2003

Technique development and measurement of Poisson's ratio, lateral creep behavior, and thermal and hygroscopic expansion of individual layers in magnetic tapes

AbstractAn experimental technique was developed to measure the Poisson's ratio (lateral contraction over longitudinal elongation), lateral creep, and both thermal and hygroscopic expansion of thin polymeric films. A so‐called profile‐matching method was developed to measure the lateral and longitudinal deformation with the help of a laser scan micrometer. A thermomechanical analyzer was used to measure the coefficient of thermal expansion (CTE). The laser scan technique was also used to measure the coefficient of hygroscopic expansion (CHE). The measurements were performed on magnetic tapes, substrates, and tapes with front coat or back coat, or with both coats stripped. A model based on the rule of mixtures was developed to determine the Poisson's ratio, lateral and longitudinal deformation behavior, and thermal expansion of the front coat and back coat. To investigate the mechanical degradation of the substrates during tape manufacturing, the data for substrate with the front and back coats removed from the tape, were compared with the data for the never‐coated virgin film. The relationship between the molecular structure and the degradation mechanism of the substrates is discussed. The magnetic tapes used in this research include two metal particle (MP) tapes and two metal evaporated (ME) tapes that use polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates. Longitudinal and lateral deformation tests were performed at 25 ± 0.5°C and 50 ± 2%RH, and thermal expansion was measured from 15 to 70°C. The CHE was measured at 25 ± 0.5°C and 15–80%RH. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2082–2096, 2003

Recording characteristics on thin metal evaporated media in a helical-scan tape system with a spin-valve head

The recording characteristics of Co-CoO metal evaporated (ME) tapes with a giant magnetoresistive head have been investigated. The reproduced spin-valve head output was 7.6 times that of an anisotropic magnetoresistive head at a recording wavelength of 0.4 /spl mu/m. We also studied the relation between the carrier-to-media noise (C/N/sub media/) ratio and remanent magnetization (Mr) magnetic layer thickness (t) in the ME tape. The media noise level was reduced with decrease in Mr /spl middot/ t by the increase of the oxygen flow rate, whereas the C/N/sub media/ ratio of the tape with a magnetic layer thickness of 33 nm was maximized at around 10 mA. We thus confirmed the feasibility of an areal density of 3.8 Gb/in/sup 2/ in a helical-scan tape drive system.

11.5 Gb/in/sup 2/ recording using spin-valve heads in tape systems

We have investigated recording at densities higher than 4.5 Gb/in/sup 2/ in tape systems using spin-valve heads. We report the signal-to-noise ratio at areal recording densities of 4.5 Gb/in/sup 2/ and 11.5 Gb/in/sup 2/ on low-noise obliquely metal evaporated (ME) tapes. Also, we studied an electrostatic discharge failure of giant magnetoresistive heads on ME tape. The results indicate the feasibility of an areal density of 11.5 Gb/in/sup 2/ in a helical-scan tape system.

Magnetic interaction fields and switching field distribution in metal evaporated tape

Interparticle interactions in metal evaporated (ME) tape were experimentally studied. The purpose of this paper is to point out that it is important to examine the angular dependence of the interaction fields to understand the magnetic properties of ME tape. The interparticle interaction is a kind of the magnetic anisotropy.

High-density reproduction characteristics with MR head for rotary drum in helical-scan tape system

A magneto-resistive (MR) head for a rotary drum in a helical-scan tape system has been developed to realize a high-capacity tape storage system with a high data transfer rate that uses a small cassette. Also, various experimental ME (Metal Evaporated) tapes whose magnetic layer thickness is 0.1 /spl mu/m or less (thin-magnetic-layer ME tapes) for the MR head has been fabricated. Reproduction characteristics of the MR head with the ME tapes was evaluated. The output voltage of the MR head was 20 times that of a conventional inductive head. An areal recording density of 1.2 Gbit/inch/sup 2/ was found to be possible combining the MR head with the thin-magnetic-layer ME tapes whose magnetic layer thickness was 0.09 /spl mu/m.

Dynamic mechanical characterization of magnetic tapes using nanoindentation techniques

The continuous stiffness measurement (CSM) technique was used to study the contact stiffness, elastic modulus, hardness, and creep behavior of a metal-particle (MP) tape, metal evaporated (ME) tapes with and without diamond like carbon (DLC) coating and a PET substrate. Nanoscratch and wear experiments were conducted using a nanoindenter with a nanoscratch attachment and a ball-on-flat tribometer, respectively. A good correlation between mechanical properties and scratch/wear damage was found. The relationship between tape structures and mechanical/tribological properties is discussed.

Long‐term mechanical and viscoelastic behavior of constitutive polymeric materials used for magnetic tapes

AbstractCreep‐compliance behavior of specially prepared magnetic tape materials was measured at elevated temperature levels to facilitate the use of a time–temperature superposition (TTS) process. This TTS process allowed for the construction of master curves at a reference temperature of 30°C, which were used to predict the long‐term viscoelastic behavior of the magnetic particle (MP) and metal‐evaporated (ME) tapes used in the study. The specially prepared samples allowed for the use of a rule of mixtures technique to determine the long‐term creep compliance of the front coat and back coat used for the magnetic tapes. To test the validity of this procedure, the front coat, substrate, and back coat data determined through separate experiments were used to calculate creep compliances of simulated tapes. These calculated creep‐compliance curves were then compared to measured data for the actual magnetic tapes. After determination and validation of the front coat, substrate, and back coat creep‐compliance data sets, they were used to determine strain distributions when the tapes are stored in a reel. Strain distributions were calculated for two cases, which reflect how tapes are stored in different drives: (1) the front coat (magnetic + nonmagnetic layer) is oriented away from the hub, and (2) the front coat is oriented toward the hub. Results showed that strain in the critical front coat of a tape is lower if it is stored with the front coat oriented toward the hub. In addition, the use of the creep‐compliance data showed that the MP tape front coat is more susceptible to creep than the ME tape front coat. The strain distributions in future magnetic tapes were also simulated by reducing the thickness and compliance of the layers. Results showed the importance of using lower compliance front coat, substrate, and back coat materials if thinner tapes are to be developed to increase the volume of information that can be stored in a magnetic tape reel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1142–1160, 2001