Tape Recording Heads Research Articles

Studies on Magnetic, Transport and Dielectric Properties of Ni0.65Zn0.35Fe2O4 Thin Films Grown by Pulsed Laser Deposition

The ferrimagnetic material Ni1-xZnxFe2O4 (NZFO) has drawn tremendous attention in recent years due to its potential applications in radio frequency coils, transformer cores, rod antennas, magnetic cores of read write heads for high-speed digital tape or disk recording and microwave devices owing to its remarkable magnetic properties, high resistivity and low eddy current. Other than these the NZFO is also considered as potential candidate for multiferroic composite structures. We have chosen Ni0.65Zn0.35Fe2O4 for the present investigation as this composition exhibits the highest saturation magnetization in the entire Ni–Zn family along with high magnetic curie temperature which is ~ 575 K. NZFO thin films were grown by pulsed laser deposition (PLD) at different substrate temperatures in the range of 500-800oC using a KrF excimer laser (λ=248 nm) on LaNiO3 buffered (001) oriented (LaAlO3)0.3(Sr2AlTaO6)0.7 substrates under oxygen pressure of 150 mTorr. These films were subsequently annealed at their respective growth temperature for 30 min in oxygen ambient at a partial pressure of ~ 300 Torr. The highly c-axis oriented growth containing only (004) diffraction peak of NZFO films along with in-plane epitaxial relationship was confirmed by high resolution X-ray diffraction measurements.From the atomic force micrographs it was observed that all the films were densely packed, smooth, free from microcrack and particulates with uniform grain-size distributions. X-ray Photoelectron Spectroscopy measurements confirmed that in all films the Ni, Zn and Fe elements retain their same oxidation states as in bulk target irrespective of growth temperature. The saturation magnetization (Ms ) of NZFO film was found to enhance systematically with increasing growth temperature. The resistance of NZFO films was found to decrease with increasing temperature indicating insulating behaviour. These films showed positive magneto resistance at low magnetic fields. Detailed dielectric, magnetic, magneto resistance and transport characterizations are currently underway and results will be discussed at the meeting.

(Invited) Linear Magnetic Tape Heads and Contact Recording

Linear tape recording heads, introduced in 1984, originally were cylindrical ferrite structures having shunt-biased magnetoresistive sensors. In 2000, heads transitioned to flat-lapped, ceramic wafers and anisotropic magnetoresistive (AMR) sensors fabricated in hard disk drive (HDD) facilities. In 2008, heads transitioned to giant magnetoresistive (GMR) sensors. Engineering tape heads has meant dealing with problems related to the head-media interface. Examples include sub-nanosecond pulses in sensors having metal shields (ca. 1994), signal losses and telegraph noise caused by parasitic electrical connections and spacing due to deposits that form at low relative humidity. Wear management, especially with 'green' media, and stick-slip effects are on-going challenges. A strategy was created for protecting GMR tape heads, leading to the discovery of polycrystalline Al2O3 films.

Head and Interface for High Areal Density Tape Recording

A tape recording head in which reading and writing functions are provided by separate modules is presented. The read-only module may be fabricated with a thinner gap than conventional read-write modules. This was shown to provide >; 40% less gap recession in a controlled wear test. Writing modules are configured to contact tape in one tape motion direction only, thus reducing the wear duty cycle twofold. Modeling indicates that broadband signal-to-noise ratio decline due to wear can be up to several dB less for the separated reading-writing head, which therefore may enable advances in linear and thus areal density.

A study of three-body particle generation and subsequent pole tip recession in linear tape recording heads

The Pole Tip Recession (PTR) and transferred material (stain) are major causes of magnetic spacing losses in magnetic recording system. The recorded signal amplitude is only independent of the data being read if the spacing is zero. Thus, the level and more specifically the variation in head media spacing with device life must be a minimum to maximise signal output and minimised errors. It was the purpose of this research to isolate and identify the mechanisms responsible for pole tip recession using the Linear Tape Open format as an experimental platform, but the results have implications for any head where the tape-bearing surface is Al 2O 3/TiC (AlTiC). All experiments were conducted within a matrix of pressure and humidity, which encompassed the system operating extremes. Atomic force microscopy (AFM) was used to analyse the surface topography of the heads and monitor the development of PTR after 100, 1000 and 5000 passes of tape. Auger electron spectroscopy (AES) was employed to analyse the chemical changes on the surface of the heads after 5000 passes of tape and X-ray Photoelectron Spectroscopy (XPS) was used to identify the chemical changes that occurred at the head surfaces. Optical Microscopy was employed to identify the head surface changes before and after wear. Environment was found to have a significant influence on the head/tape interface. Head wear and PTR were highest at high temperature and humidity. Wear between the head and tape was found to transform the surface layers on the TiC grains in the tape-bearing surface to TiO 2. This process results in the production of TiO 2 fragments that become trapped in the recessed pole tip region, acting as three-body abrasive particles. The presence of Ti on the surface of head thin film region confirmed that the three-body particles originated from the head AlTiC ceramic. The TiO 2 (thickness and possible areal coverage) increased with the water content increase, wear of head increased in the high water content condition.

Contact noise in magnetoresistive read sensors for ultrahigh-density flexible media applications

Measurement of the cooling induced noise in magnetoresistive tape recording heads is reported. This form of is produced by temperature reduction of the sensor when tape surface irregularities contact the element or shields. Contact scales quadratically with element temperature and places constraints on the maximum attainable areal density using anisotropic magnetoresistive tape heads.

Hard-disk-drive technology flat heads for linear tape recording

IBM thin-film tape heads have evolved from the ferrite-based heads first used in the IBM Model 3480 Tape Drive to the hard-disk-drive (HDD) technology flat-profile heads used in IBM Linear Tape-Open® (LTO®) products. This paper describes that transition and discusses the flat tape head manufacturing processes, drive implementation, performance, and outlook. Thin-film head technology for hard-disk drives was first used in tape heads in the early 1990s, when IBM built quarter-inch cartridge head images on HDD-type wafers. This was a springboard for the next step, flat-lapped tape heads, which use not only HDD wafers, but also HDD post-wafer machining technologies. With the emergence of LTO, flat heads entered mainstream tape head production in IBM. These have proven to have high performance and durability.

Flat-profile tape recording head

In conventional recording, tape wraps a cylindrically contoured head. The authors describe an implementation in which tape contacts a flat-profile bidirectional recording head. Magnetic transducers are located away from the air-scraping edges in the region of uniform head-tape spacing. Optical measurements on glass heads confirm intimate contact between head and smooth media below approximately 3 m/s. Wallace spacing losses show an increase with tape speed, but contact is still evidenced by head wear at 6 m/s. Air leakage and tape mechanical effects lift the tape edges. The width of the lost-contact region is controlled by the design. Flat heads are fabricated using hard-disk-drive head materials, methods, and facilities, and are implemented in the IBM TotalStorage 3580 Linear Tape Open Ultrium drive.

Recording performance and tribological evaluation of FIB defined tape recording heads

Aggressive growth in cartridge capacity in future generation tape drives requires amongst others, high linear recording and track densities. In order to improve the track misregistration (TMR) budget at smaller track pitches, the erase band and tolerances on the recorded track width need to be minimized. This can be achieved by "trimming" the write element to the desired track width by forming a longitudinal channel on either side of the clement on the tape bearing surface (TBS) using focused ion beam (FIB) milling. Cross-track measurements depict desired track widths with reduced forward-reverse track width asymmetry in the read-write-read head configuration. Investigation of the head/tape interface does not predict any undesirable effects. These channels capture debris and hence will reduce the recording loss, especially at higher linear recording densities, due to tape tenting over loose debris transported through the interface and near the recording elements. A conceptual channel design is presented that will further reduce debris near the recording elements during the life of the head.

Video tape recorder head inspection using image processing techniques

In currently selling video tape recorders (VTRs), two or more heads fixed at a revolving drum are used to record or reproduce video signals. To obtain uniform quality, the video heads should have similar characteristics such as geometrical shape and electromagnetic performance. This research is designed to develop a visual inspection system that can measure four geometrical parameters. To obtain reliable results, a digital signal processing-based image board and target-based imageprocessing algorithms were used. A series of experiments were performed on 1000 video heads. From observation of the experimental results, except for the cases of noise on the head and cracklike defects, we were able to obtain high inspection reliability, with an error bound within ±5 ?m.

TMR window measurements with thin film write/MR read heads on metal particle tape including erase bands

A method for measuring track widths of narrow track tape recording heads for use in track misregistration models is reported. The method involves using the azimuth displacement technique with prerecorded metal particle tape to acquire crosstrack and erase profiles of read and write elements in the recording head. A signal to noise ratio analysis is then used to obtain values of track widths that can be used directly in a track misregistration model.

Trends in digital magnetic recording; the application of thin-film heads for tape recording

Digital tape recording systems show the same trend as hard-disk drives: a large increase of storage density with time. The use of advanced media and highly sensitive thin-film heads with magnetoresistive (MR) readout will increase the storage density dramatically. Key improvements are narrower tracks, more sensitive MR elements attained by applying the giant magnetoresistance effect, high-saturation flux density pole materials, advanced metal powder tape, intimate head-to-tape contact, and accurate tracking. By increasing the number of channels in the multitrack thin-film head, high data rates can be obtained as well. The basics of digital magnetic recording are discussed and a short historical overview is given of the Philips activities on thin-film heads for tape recording. An outlook on future improvements is given.

Thin-film heads with anisotropy-determined track widths

Multitrack yoke-type MR readout heads having a single shared front fluxguide with a highly anisotropic permeability, have been designed and evaluated. The well defined microtrack response profiles of these heads show that the anisotropy of the permeability confines the flux-detection to the area on tape in between the contact leads of the MR element. This can be exploited in "full-density" tape recording heads which read directly a number of adjacent tracks.

Blocking of magnetization ripple in FeAlN thin film tape heads

In this paper we present domain images on the pole tips of thin film tape recording heads using high moment FeAlN pole materials (4/spl pi/M/sub s/=20 kGauss). These heads are of the type used in quarter inch cartridge (QIC) tape drives, with a record gap dimension of 1.9 /spl mu/m, a written trackwidth of 33 /spl mu/m, and a 14 turn coil. The pole thicknesses ranged from 4 to 4.5 /spl mu/m. These heads exhibited domain structures on the pole tips indicative of the blocking of magnetization ripple seen in sheet films of soft magnetic materials with thicknesses less than 1000 /spl Aring/.

Exchange-biased spin-valves for magnetic storage

An overview is given of the material properties of exchange-biased spin-valves. More specifically, we discuss the microstructure and magnetic properties of these materials as relevant for (future) industrial application in magnetoresistive read heads for rigid disk and tape recording and Magnetic Random Access Memory (MRAM) devices.

Comparison of mechanical and tribological properties of permalloy and high moment FeTaN thin films for tape recording heads

This paper reports experimental results of a comparative study for mechanical and tribological properties of permalloy (NiFe) and magnetically soft high moment FeTaN sputtered thin films. It was observed that the hardness, elastic modulus and wear resistance of FeTaN films are all superior to those of NiFe permalloy films. AFM observations on unworn films and worn surfaces of a wear scar revealed that pit formation may contribute to wear damage mechanisms for low load abrasive wear.

Thin film tape recording heads with high moment FeAlN poles

In this paper we present results on the fabrication and testing of thin film tape recording heads using high moment FeAlN pole materials (4/spl pi/M/sub s/=20 kGauss). These heads are of the type used in quarter inch cartridge (QIC) tape drives, with a record gap dimension of 1.9 /spl mu/m and a written track-width of 33 /spl mu/m. The pole thicknesses ranged from 4 to 4.5 /spl mu/m with a 14 turn coil. The FeAlN pole material delivers sufficient field to the media surface to saturate 1.5 /spl mu/m thick Ba-Ferrite media (H/sub c/=1500 Oe). In comparisons to a head of identical design with CoZrTa poles, the FeAlN poles were able to deliver more flux to the media because of a higher head saturation onset current.

Propagation of Boundary Disturbances in an Axially Moving Strip in Contact With Rigid and Flexible Constraints

The exact expression describing the contact force between an axially moving flexible strip and a one-sided constraint is derived using the Green’s function formulation. Discontinuity of the initial velocity at a boundary of the strip due to a disturbance, causes discontinuity in the contact force history at any constraint that is not modeled by a single spring element. The discontinuities in the contact force occur at the instants when those propagating wavefronts in the strip with nonvanishing slope interact with the constraint. A model of a magnetic tape-recording head system is analyzed. Tape-head contact loss is predicted, depending on the amplitude and frequency of a disturbance, the head location, and the preload of the tape against the head.

Photothermally modulated readback from a magnetic tape

The photothermally modulated (PM) readback technique is based on the thermal modulation of a recorded magnetic pattern. The PM-readback signal that is detected by a conventional tape recorder head comprises lateral and depth resolved information of the recorded signal. The PM-readback has been studied from homogeneously magnetized tapes and from a sinusoidal track recorded on a CrO/sub 2/ tape. From the signals measured as a function of laser spot position and of modulation frequency the depth and lateral variation of the magnetization has been determined.

Measurement of head wear rates using custom high sensitivity electrical elements

A technique for measuring the wear rate of a tape recording head is described that can produce a theoretical dimensional resolution of 0.02 nm. Custom four wire elements are located in the gap of the actual recording head design to be tested (rather than using substitutes) and can be strategically placed to measure the wear rate across the width of the tape. Temperature compensation is achieved by measurement of a spare identical element in the head structure set back from the wear surface such that it does not receive wear. The wear rate at various locations across the head gap lines of NiZn ferrite heads have thus been obtained continuously as a function of the amount of CrO/sub 2/ tape passed and show that the wear rate is greater near the tape edges. Due to the high sensitivity of the test elements, use of long reels of tape and placement of multiple heads in the same tape path, comparisons of head contour shape and/or materials can be made in a very short test time.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Performance comparison of unshielded and shielded MR read heads for digital tape recording

The authors report data comparing a shielded magnetoresistive head (SMR) optimized for metal particle tape readback to an unshielded head (UMR) with an identical element. They identify the signal-to-noise ratio penalty for eliminating the shields as a function of tape velocity and data density. They report on the degree of nonlinear distortion for UMR and SMR heads with and without write equalization. From these experiments the performance of an element optimized specifically for the absence of the shields is predicted. An unshielded sensor can be a satisfactory replacement for an SMR sensor at linear densities up to 2500 fr/mm, provided it is redeveloped for optimum signal amplitude and linearity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>