Thin-film Recording Heads Research Articles

Micro- and nanoscale thermal phenomena in thin-film magnetic recording heads

As the magnetic data storage industry continues to pursue aggressive miniaturization of sensors and write elements in thin-film recording heads, it faces serious thermal management challenges. The present work develops theoretical models of heat conduction and power dissipation in current-in-plane and current-perpendicular-to-plane sensors to highlight key physics and help examine the influence of various parameters. Fundamental physics of heat conduction in thin films and across interfaces is discussed to facilitate systematic exploration of novel high thermal conductivity materials and methods to minimize the thermal interface resistance. Experimental techniques for thermal characterization of recording heads and constituent thin films are also presented.

Micromagnetic study of side-writing phenomena using thin-film heads and Co–CoO metal-evaporated tape

The recording process and the relationship between the side-written band and the pole shape of thin-film recording heads, which have an upper pole with a narrow track width and a trimmed lower pole, using Co–CoO, obliquely evaporated magnetic tape, have been investigated. In nonazimuth recording, the lower pole of the thin-film head on the trailing side is better than that on the leading side for generating a sharp-edged, side-writing band. In azimuth recording, the relationship between side-writing phenomena and the pole shape of a thin-film head is complicated, because the position recorded by the leading gap-field shifts across the track width from that recorded by the trailing gap-field due to the azimuth angle. The thin-film recording head with trapezoidal upper and lower poles to minimize the effect of the side-fringing field can generate a sharp-edged, side-writing band, particularly in azimuth recording, but it is critical that the lower pole be on the trailing side. The thin-film recording head, which has a trapezoidal upper pole on the leading side and a trapezoidal lower pole on the trailing side, is most effective in generating a sharp-edged, side-writing band.

Analytic field components for perpendicular thin-film recording heads

Presents a new, entirely analytic solution for the magnetic field of a thin-film head of arbitrary dimensions in the presence of a soft magnetic underlayer. The magnetic potential on each pole is assumed to be a known constant. Fourier coefficients and field components are given for two particular cases of practical interest. The paper demonstrates the accuracy of approximations that require no Fourier coefficients, but that must be evaluated numerically.

Effect of damping constant on the switching limit of a thin-film recording head

This article presents a micromagnetic study on the dynamics of magnetic flux transfer in the pole tip region of a stitched-pole magnetoresistance/thin-film head. Three-dimensional vortices are found inside the pole tips. The flux at the ABS surface is conducted by the motion of the vortex moving in the cross-track direction. The resulting head field well follows the driving flux with little phase delay and little dependence on the damping constant, α. The vortex motion under the driving flux maintains similar speed even when the damping constant is decreased to zero. In this case, it is found that in addition to the motion of the vortex, spins precess locally with small cone angles, resulting in small head field fluctuations. It is concluded that the speed of magnetization flux reversal in the pole tip region is not limited by small damping constant.

Development of high coercivity magnetic force microscopy tips

We report on the fabrication of high coercivity magnetic force microscopy tips for magnetic images. The CoPt permanent magnetic crystallites are prepared by magnetron sputtering followed by annealing at 700°C in an argon atmosphere. We present the magnetic images of a thin-film recording head and written patterns of a recording disk taken with high H c CoPt MFM tips.

Future directions in electroplated materials for thin-film recording heads

The need for recording heads to write on high-coercivity media at high frequencies has created new requirements for the write-head material that cannot be met by Ni <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">80</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</inf> , the nickel-iron alloy traditionally used in the fabrication of the device. Electroplating through a mask, the method of choice for depositing nickel-iron alloys, makes it possible to pattern and orient the magnetic film more readily than by other methods. We review here research performed mostly in the United States and in Japan to develop electroplated magnetic materials that can meet the new challenges of data storage technology. High-iron nickel-iron alloys (Ni <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">45</inf> Fe <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">55</inf> ) have higher magnetic moment and resistivity than their low-iron counterparts and are increasingly being used in head fabrication. The addition of impurities in a controlled manner has been shown to produce drastic improvement in the properties of electroplated materials. And technology has been developed to fabricate laminated materials by electroplating from a single plating solution. Despite these advances in the electrodeposition of magnetic alloys, more research is required for electroplating processes to meet all of the challenges of data storage technology.

Soft-magnetic fluxguide materials

This paper reviews the research done on soft-magnetic fluxguide materials for use in sandwich heads and in thin-film recording heads for digital magnetic recording. After dealing with the basic principles of magnetic recording, the requirements on modern soft-magnetic materials are discussed. The roles of magnetic anistropy and magnetostriction in relation to permeability are discussed. Next, we review the recent advances in soft-magnetic materials processing, in particular for amorphous cobalt (CoNbZr) and nanocrystalline iron alloys, such as FeMX, with M being group IVa-Va metals such as Zr, Hf, Nb, Ta, etc., and X being N and O.

High resolution imaging of thin-film recording heads by superparamagnetic magnetic force microscopy tips

We have used superparamagnetic magnetic force microscopy (MFM) tips to obtain high spatial resolution MFM images of recording heads. Profiles of the magnetic field gradient above a thin-film recording head under 3 mA bias current to the head and various tip-head distance conditions are presented. At a low tip-head distance, the gap width, gap location, and gap-field structure can be well resolved in these MFM images. Superparamagnetic tips show promise for the magnetic imaging of recording heads with gap widths below 200 nm.

Micromagnetic modeling of thin-film recording heads

As recording heads become smaller to achieve higher recording densities, their domain structure increasingly influences their performance. Due to the presence of closure domains in the head, for track widths the order of 1 /spl mu/m, the available head flux becomes limited and the asymmetry in the flux geometry is increased. To study the problem, this paper presents some micromagnetic calculations on thin-film recording heads. The model computes the domain variations in the head when a field is applied for both permalloy and iron-nitride. It is found that the flux asymmetry is small for small fields, increases to a maximum, and finally disappears at saturation. Possible designs that could reduce this effect are discussed.

Thin-film inductive heads

The development of IBM thin-film inductive recording heads is traced from 1964, through their first introduction in 1979, to the present. We review a number of innovations in thin-film technology materials and processes associated with this type of head. Design and technology changes made since 1979 have led to the development and implementation of heads in several successful recording systems. We also describe efforts to predict the performance of thin-film inductive heads and to understand and control head instabilities and noise.

Theory, fabrication and testing of dual track complimentary type of thin-film recording heads for perpendicular magnetic recording system

A new type of recording head for a perpendicular magnetic recording system, a dual track complimentary (DTC) type of thin-film head, was proposed in this study. The magnetic core of the head has a ‘‘U’’ character shape which is provided with ‘‘a pair of’’ recording tracks and the efficiency to detect flux reversal in the media will become high enough to achieve high linear density. The two-dimensional analysis of DTC heads implied that the perpendicular component of the head field should become larger by using the double-layered media under a narrower spacing condition. Recording characteristics using conventional ring head were evaluated in order to determine the principle of DTC configuration. Several DTC heads were prepared using photolithography technique and their performances were examined. A typical DTC head has inductance of about 500 nH, which is relatively low, and constant up to 10 MHz. DTC heads seems to be one of the most hopeful candidates as the heads useful for perpendicular magnetic recording systems.

Rapid Thermal Magnetic Annealing: A Novel Technique in Thin-Film Recording Head Production?

AbstractA new emerging application area for Rapid Thermal Annealing (RTA) may be in the manufacturing of thin-film recording heads for high-density (hard disk drive, video, audio and data tape) recording. To that end we co-designed a new commercial reactor with an external electromagnet to anneal thin soft-magnetic films (nanocrystalline iron alloys) deposited on ceramic wafers of up to 150 mm diameter. The electromagnet generates a field controllable up to 660 Oe (52.8 kA/m). It is completely homogeneous in direction (i.e. fully parallel field lines) across the entire wafer area. Wafers can be annealed either statically, or while rotating (up to 120 rpm), or in two subsequent heating steps with a 90° wafer rotation in between.Nanocrystalline Fe-Nb-Si-N layers have better soft-magnetic properties after Rapid Thermal Magnetic Annealing (RTMA) in a static magnetic field than after conventional furnace annealing in a static field. Temperature-programmed resistance measurements and Transmission Electron Microscopy (TEM) show that the first nanocrystalline, body-centered cubic iron grains start growing already as of 350 °C from the amorphous as-deposited film, whereas the desired segregation of NbN starts only as of 530°C. RTA can be used to promote the kinetics of the segregation of NbN along the boundaries of nanocrystalline iron nuclei. This prevents the iron grains from further growth: with RTMA the iron alloys show smaller nanocrystalline iron particles (order: 10 nm) as observed by TEM.

Development of hard carbon coatings for thin-film tape heads

Major problems in thin-film recording heads are pole tip/gap recession in the inductive head and scratching/smearing, electrical short, electrostatic charge build up, and corrosion of the MR stripe in the MR heads. Wear of head structure can be minimized by depositing a hard carbon coating over the entire ABS including the head structure. In this study, we have deposited carbon coatings on Ni-Zn ferrite and Al/sub 2/O/sub 3/-TiC substrates and dummy heads by various deposition techniques and characterized for mechanical and tribological properties. Ion beam carbon coatings on Ni-Zn ferrite and cathodic arc carbon coatings on Al/sub 2/O/sub 3/-TiC heads exhibit most wear resistance compared to other coatings in a tape drive test.

微細加工技術と表面処理 薄膜磁気ヘッドにおける微細加工技術

微細加工技術と表面処理 薄膜磁気ヘッドにおける微細加工技術

Dc magnetic force microscopy imaging of thin-film recording head

Using a new form of magnetic force microscope (dc MFM) magnetic force images of a thin-film recording head have been made. Using dc MFM, atomic force microscope images are presented of the surface topography and magnetic forces taken simultaneously, allowing direct correlation of magnetic fields to the pole pieces. Magnetic force images of the head at typical head-to-disk spacings are presented. The tips used for these images had two different magnetic coatings.

High frequency head and playback model for thin-film recording heads

A thin-film head field and readback model that allows for eddy currents has been proposed and used to compute complex head efficiency, inductance, anomalous (ac) resistance, head saturation fields and locations, as well as the digital playback parametrics high and low frequency amplitude, resolution, PW-50, and maximum overwrite fields with a fair amount of accuracy. The head model solves for the time-dependent vector potential in a geometry that closely resembles a modern three dimensional thin-film recording head, including variable pole and yoke width, thickness, permeability, resistivity, neck angle and other geometrical parameters. Readback emulation is done with a discrete Fourier version of the reciprocity integral using Szczech fields and arctan transitions, along with complex efficiencies from the head model. Detailed comparisons with experimental observations are given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Magnetic instability of thin-film recording heads

Two forms of magnetic head instability are investigated: Write and read instability. Write instability generates noise directly after writing which impairs sector-servo performance. This noise peaks at write currents saturating the apex or backgap. The noise amplitude is exponentially distributed. The noise is caused by cooling off of the yoke after write as well as by thermally activated domain wall jumps in the upper yoke. Read instability produces read pulse distortion, predominantly on the signal's trailing edges. The only form of instability in dedicated-servo drives, read instability is best characterized by pulsewidth measurements. The degree of instability changes with intermediate writes. Read instability is caused by hysteretic domain wall motion in the pole tips in response to signal excitation and/or stray magnetic fields. >

Dual Track Complimentary Type of Thin Film Recording Heads for Perpendicular Magnetic Recording

Dual Track Complimentary Type of Thin Film Recording Heads for Perpendicular Magnetic Recording

Recording asymmetries at large skew angles

The effect of head skew on the read, write, and erase properties of thin-film inductive recording heads is explored. Using novel track profiling methods, combinations of large skew angles and small recorded wavelengths were found to cause offtrack displacement of written transitions and asymmetric erase bands. The maximum offset measured was 0.3 mu m at 35 degrees skew and a 1.7 mu m wavelength. Increased side reading in the opposite direction to the write process offset was also observed. These asymmetries are expected to increase the likelihood of track misregistration errors in a drive environment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Phase lag in the high-frequency response of thin-film recording heads

The phase lag introduced by a head in the writing process was measured with a scanning Kerr effect microscope. The phase lag of thin-film heads increases rapidly with frequency even below 30 MHz. A 20 degrees phase lag at about 20 MHz was observed on both an IBM 3380 eight-turn and a 3390 31-turn head. By studying the phase lag caused by different damping mechanisms in the magnetization processes, it was concluded that the rapid increase in phase lag below 20 MHz is primarily caused by the damping of domain wall motion in the sloped region. Different designs of the sloped region of the heads were shown to cause large differences on the phase lag. The effect of drive current amplitude on the phase lag was studied both experimentally and theoretically. The results indicate that, when eddy current damping dominates and the surface of a magnetic film is driven to saturation, a larger phase lag occurs when larger drive field is applied.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>