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This paper describes experimental spin-stand tests of a narrow-track differential head, reading back square-wave patterns on longitudinal and perpendicular recording media. The low linear density response of the transducer to recording signals of longitudinal and perpendicular media consisted of bipolar and unipolar pulses, respectively. The paper also presents the head responses to dibits and magnetic patterns recorded in longitudinal media. The head attained the highest linear resolution with a longitudinal thin-film medium, having an areal magnetic moment of [M.sub.r] [delta] = 0.5 memu/[cm.sup.2] and a coercivity of [H.sub.c] = 3.0 kOe. The nominal full dynamic range of the transducer was tested with a longitudinal medium having [M.sub.r] [delta] = 1 memu/[cm.sup.2], but at the expense of a lower linear resolution. The transducer showed a considerably lower linear resolution, when reading back magnetic patterns of a dual-layer perpendicular medium. The experimental time-domain and spectral responses of the dual magnetoresistive head agreed well with those predicted by theory. Index Terms--Differential magnetoresistive head, dual magnetoresistive head, magnetic recording heads, magnetoresistive heads, perpendicular recording.

This paper discusses the advantage of utilizing a Co/Ru/Co synthetic antiferromagnet in the fabrication of spin valve heads suitable for high density magnetic recording. Benefits of using the synthetic antiferromagnet are: (1) the pinning field is over 6000 Oe; (2) magnetic stability is achieved over a wide temperature range with the sensor well biased at temperatures as high as 250 [degrees]C, because the pinning field is still higher than 3000 Oe at this temperature; (3) the pinned layer biasing mechanism is enhanced as the sensor height is reduced, and a 7.2% change in the resistivity is observed in a sensor with a 0.5 [[micro]meter] height and a 0.7 [[micro]meter] trackwidth; (4) the free layer bias state is easily attainable in sensors with small height (< 1 [[micro]meter]), as a consequence of the particular magnetic configuration of the synthetic antiferromagnet, which promotes an almost vanishing magnetostatic field; and (5) the sensor is only 17 nm thick. Index Terms - Magnetic recording, magnetoresistive materials, spin valve sensor, synthetic antiferromagnetic bias layer.

This paper reviews the material properties of FeAlN high moment soft magnetic material, and discusses the design, fabrication and performance of write heads using this material. These write heads comprise of two designs. The first had FeAlN for both top and bottom poles. The second incorporated a 0.2 [[micro]meter] thick FeAlN layer underneath an electroplated [Ni.sub.80][Fe.sub.20] top pole. The first type of heads was tested on high coercivity (3300 Oe) media. Wide and narrow track width heads saturated the media at the highest tested write frequency of 225 MHz. At 90 MHz, they exhibited overwrite approaching 50 dB and hard transition peak shift of less than 1 nm. This overwrite was 7-9 dB higher than that measured for heads with [Ni.sub.45][Fe.sub.55] top poles. A 50% amplitude roll-off density ([D.sub.50]) of up to 6300 fc/mm was also measured, using a narrow gap MR read sensor. However, reverse dc erase noise measurements indicated significantly lower head efficiency compared to NiFe heads, as has been observed previously. The second type of heads on the other hand exhibited [approximately]5 dB better overwrite compared to a [Ni.sub.80][Fe.sub.20] head, without a large loss in head efficiency. Index Terms - FeAlN, magnetic write heads, recording head fabrication, recording head material.

Giant-magnetoresistance ratios greater than 5% are found in spin valves exchange biased by a Co/Ru/Co synthetic antiferromagnet, according to room temperature measurements. Fields greater than 5000 Oe are required to saturate the synthetic antiferromagnet. Using a Co/Ru/Co synthetic antiferromagnet can boost the thermal and magnetic properties of a spin valve when the traditional exchange layer is replaced by the synthetic antiferromagnet. It is possible to have synthetic antiferromagnet based spin valves working at temperatures higher than 250 degrees C.

Experimental thin film inductive heads using previously developed laminated FeAlN high moment soft magnetic materials have been designed, and fabricated to the wafer level. The heads, with a gap length of 0.2 [[micro]meter] and trackwidths varying from 6 to 84 [[micro]meter], were fabricated with a mainly dry process. The dynamic domain patterns of the top magnetic poles were observed with a high speed wide-field Kerr microscope. Closure domains were not present, while multiple easy-axis domains were observed in the head yokes. The head inductances were measured from 1 to 50 MHz with a network analyzer. The electrical and magnetic testing results show that the fabricated heads function well at the wafer level and that laminated FeAlN high moment material is a very promising candidate for future high-density recording head applications.

Praseodymium-substituted garnet films are investigated to determine the magnetic properties, growth conditions and low-field ferromagnetic resonance properties of the films which have a chemical composition of YPrLuFeO. The films are grown by liquid phase epitaxy on (III)-oriented Gd3Ga5O12 substrates. The properties enable the measurement of cubic anisotropy and saturation magnetization.

The magnetic characteristics of FeAlN/SiO2 and FeAlN/Al2O3 multilayered thin film structures were investigated for recording head applications. The results showed that the two samples have reduced coercivity and increased roll-off frequencies. However, Al decreased the saturation magnetostriction constant and shifted the minimum coercivity point to a higher N content.

Three-dimensional modeling was performed to show that integration of a single-pole head with a relatively wide leading pole and a medium with a soft underlayer (SUL) gives rise to the field multiplication effect due to the 'multiple image reflection' of the flux generated in the hard-layer region located between the leading pole and the SUL. Magnetic force microscopy and spin-stand experiments were utilized to support the theory. Index Terms--Magnetic mirror, multiple image reflection, perpendicular recording.

The performance of spatially resolved ferromagnetic resonance (FMR) with a proposed measurement technique is discussed. The decline in the number of nodes due to an increase in the bias field and the appearance of quantized magnetostatic mode waves at certain bias fields is observed.

Magnetic and thermal properties of Co(sub 0.5)Ni(sub 0.5)O, NiO and IrMn when exchange coupled with NiFe were investigated as a function of antiferromagnet thickness. Blocking temperatures of antiferromagnet/ferromagnet exchange couples were shown to be dependent on thickness and deposition conditions of the antiferromagnet. The antiferromagnets' thickness dependence observed a power-law type of relation, consistent with a finite-size-effect.

A study was conducted to analyze the magnetic characteristics of CrPt3 L12 ferrimagnetic thin films. The films were prepared by sputtering multilayers of chromium and platinum onto silicon nitride coated silicon substrates. Results indicated that the films supported large coercivities that can be tuned between 1,500 to 8,000 Oe. Findings also showed Kerr rotations of about 0.21 degrees when the films were overcoated with a quarter-wavelength dielectric.

The perpendicular fields emanating from an ultra small perpendicular single pole head have been quantified using a new MFM field mapping technique. This technique utilizes two MFM tips with different field sensitivities which have been focused ion beam etched to identical geometries. This technique has been used to quantify the perpendicular fields around a 100 x 200 nm pole, also fabricated with focused ion beam etching.

The initial permeability of NiFe single layer films and single and multi-layer FeAlN films up to 500 MHz are presented. The permeability of thin ( Index Terms - FeAlN, high frequency permeability, recording head material, transverse bias permeability.

In this work, the device level properties of GMR-DMR read-elements (REs) fabricated from an antiferromagnetically coupled continuous multilayer, that exhibited large giant magnetoresistance, are characterized. REs having stripe heights of 1 and 2 [[micro]meter] and a trackwidth of 3 [[micro]meter], were characterized in terms of self stabilized single domain state, electric/magnetic homogeneity and sensitivity to spatial gradient fields. A simple two-parameter model of the interlayer coupling in the GMR multilayer film, fit to only the sheet film MR loops, was combined with micromagnetic simulations to fairly accurately predict the experimental curves obtained with the REs. Temperature effects due to Joule heating at higher sense currents were accounted for in the theoretical curves, by using measured resistance and GMR ratio variation with temperature. Projections of the performance of a GMR-DMR head that uses a similar multilayer film are presented. Index Terms - Antiferromagnetically coupled multilayer, Dual magnetoresistive head, Giant Magnetoresistance Ratio.

The magnetic properties of IrMn when exchange coupled to NiFe have been investigated as a function of composition and sputtering parameters.Temperature stability has been studied with regard to IrMn thickness and corrosion properties were measured and compared with FeMn, CoNiO, and NiMn. The NiFe based spin-valve structures which were fabricated with IrMn, showed good magnetic properties

A thin metal mask is desirable when defining narrow structures by ion milling. This article explores the definition of narrow high moment iron nitride inductive head pole structures by ion milling in Ar/[O.sub.2] and Ar/[N.sub.2] gas environments through a Ti mask. Modest ion milling selectivities between Ti and the iron nitrides (FeAlN and FeTaN) were achieved by ion milling in Ar/[O.sub.2], although the mill rate of the iron nitrides was reduced dramatically. Selectivities of over 4 were achieved by ion milling in Ar/[N.sub.2] ambient, without severely reducing the ion milling rates of the iron nitrides. Hence this reactive mill process is a viable method for defining narrow iron nitride poles by ion milling at the wafer level.

The effect of structural imperfections such as interface roughness and layer strain on the sign and amplitude of the interlayer coupling between the two ferromagnetic layers of exchanged-biased NiFe/ Cu/ NiFe/ FeMn spin valves is discussed. Two distinct regimes are found: when the NiFe-Cu interface is smooth, with a mean roughness smaller that 4 [Angstrom], the interlayer coupling shows a distinct oscillatory behavior, with a period of [Lambda] = 13.5 [Angstrom], and can be well described by a RKKY-like exchange based mechanism. As the amplitude of the interface roughness increases the magnetostatic-type Neel's orange peel coupling becomes more important, and the ferromagnetic component of the coupling is enhanced. The higher than expected period of oscillation, observed in these spin valves, is explained in terms of a strain induced effect.

Tri-layer structure MSR disks were fabricated and tested using a center aperture detection method. The disks consisted of a GdFeCo read-out layer, a TbFeCo recording layer, and a GdFe intermediate layer. Two samples were prepared with 15 nm and 7.5 nm GdFe thicknesses and one sample contained no intermediate layer. The read-out waveform for the sample with the 15 nm GdFe layer was observed to approach zero in the range 3.3 mW < read-out power ([P.sub.r]) < 3.5 mW and change polarity when Pr > 3.5 mW. This anomalous behavior is believed to be the effect of exchange coupling (EC) forces dominating at temperatures below [T.sub.Curie] of GdFe and magnetostatic (MS) forces dominating above [T.sub.Curie] of GdFe. Therefore, the read-out signal approaches zero when the EC and MS forces are equal in magnitude. This phenomenon was not observed for the sample with 7.5 nm GdFe nor for the bi-layer sample.

Thin film inductive write heads with track-widths down to 0.7 [[micro]meter] were fabricated by trimming wide track-width heads using focused ion beam etching from the slider air hearing surface. These heads incorporated FeAlN high moment pole material. They were observed to saturate media with coercivity of 2950 Oe. In this work, magnetic force microscopy (MFM) is used to evaluate tracks written by these heads. Sharply defined track edges were observed even for the narrow track-width heads up to high linear density. Simulations using accepted models for wide track writing agree with some of the experimentally observed trends for the submicron tracks.

Polycrystalline [Dy.sub.1.6][Bi.sub.1.4][Fe.sub.(5-x)][Ga.sub.x][O.sub.12] and [Gd.sub.2]Bi[Fe.sub.(5-x)][Ga.sub.x][O.sub.12] garnet thin films have been deposited on glass substrates by metallo-organic decomposition. The advantages of this process include low cost and accurate control of composition. The crystalline garnet phase was ascertained by x-ray diffractometry and the composition was measured by x-ray flourescence. The magnetic and magneto-optic properties were characterized using a magneto-optic loop tracer.

Perpendicular recording probe heads using high moment FeAlN/NiFe laminated magnetic materials as poles were fabricated and tested. FeAlN/NiFe films with a saturation magnetization of 18 KG, a coercivity of 1.0 Oe, and an anisotropy field of 8 Oe, were developed for application in Micro Flexhead[TM] components. When tested on CoCrTa/NiFe double layer disks, the high moment heads showed superior overwrite performance and nearly equivalent isolated pulse width compared with typical CoZrNb heads. Vertical domain walls perpendicular to the as-deposited easy-axis of the poles were observed with a scanning magneto-optic photometer and correlated to the read amplitude variations.

In this work, the advantage of the antisymmetric dual magnetoresistive head (A-DMR) in comparison to the symmetric design (S-DMR), in terms of common mode longitudinal field rejection is demonstrated experimentally. The experiments were conducted at the wafer level. Magnetoresistive hysteresis loops of the heads with the top permalloy longitudinally biased by TbCo exchange tabs, defined either by an ion-milling process or by lift-off are presented. Initialization methods to have the symmetric or the antisymmetric state at low longitudinal applied magnetic fields are described.

Rapid thermal annealing reduces crystal grain sizes of bismuth-doped iron garnet films developed on glass substrates. The reduced grain sizes enhance thermomagnetic circular domain organization, carrier-to-noise ratio, garnet phase nucleation and grain growth inhibition at high temperatures in the films, resulting in the resolution of noise problems in the magnetic media systems.

Praseodymium (Pr)-doped iron garnet films demonstrated magnetic and low-field ferromagnetic resonance properties, which were studied as a function of doping content. Pr was added to the garnet films to enhance soft magnetic properties. Pr- and Lu-doping had negligible influence on saturation magnetization at ambient temperatures.

Multidomains constitute the domain configurations on the air-bearing surface (ABS) of inductive thin-film recording heads. The direction walls are not related to the gap plane and magnetization occurs in the plane of the ABS along the track width. Magnetic charges are spread by the domain walls resulting in reduced magnetostatic energy.

Analysis of dynamic domain instability revealed that thin-film heads exhibit two different processes of popcorn noise. Both processes are caused by thermal transients after the write. The low and exponentially enhancing popcorn noise probability is caused by the macroscopic wall jump process.

Amorphous sputtered films produced crystalline barium ferrite films that exhibited in-plane magnetic anisotropy when subjected to postdeposition annealing. The presence of physical voids or channels that separated the grains in these films reduced exchange coupling. Barium ferrite exhibited the magnetic and recording characteristics required for flexible media.

The phase lag introduced by a head in the writing process was measured with a scanning Kerr effect microscope. It was found that the phase lag of thin-film heads increases rapidly with frequency even below 30 MHz. A 20 degree phase lag at about 20 MHz was observed on both an IBM 3380 8-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 in the phase lag. The effect of drive current amplitude on the phase lag was studied both experimently 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. In some cases, overdriving can even cause a decrease in the response of a head. The phase lag caused by the heads in the reading process were studied by measuring two heads coupled together through their air- bearing surfaces, and the results suggest that there is more phase lag in the reading process than in the writing process.

The effects of high temperature long-term aging on the erasability of various high coercivity tape media were investigated. The results showed that Co-Gamma-Fe2O3 media, depending on how they were prepared, could become increasingly harder to erase, or stay virtually unchanged in their erasability after prolonged aging. For CrO2 media, experiments indicated that aging the media at high temperatures could cause severe corrosion, which badly degraded the media magnetic properties and recording performance, as well as altered the media erasure characteristics. Much less severe corrosion was observed for metal particle media. Aging the metal evaporated media at high temperatures caused their coercivity to increase, by as much as 30%, which was also reflected in the media erasure characteristics. Of all the media studied, Ba-Ferrite were found to be the most stable media against the annealing process.

The erasure and noise characteristics of longitudinally-oriented barium ferrite tape media with varying squareness values were investigated. The results showed that samples with high squareness values were easier to erase using longitudinal fields and harder to erase with vertical erase fields than the samples with low squareness values. At the highest squareness value, longitudinal dc fields were more effective than longitudinal ac fields.

The characteristics of magnetization patterns on rigid thin film disk media with wavelengths ranging from 20 to 1 micrometer were investigated using magnetic force scanning tunneling microscopy. The results showed that there were two major effects to which signal loss was attributable: magnetization reduction and the formation of bit clusters in the material. The tracks gradually lost their ability to retain the recorded pattern as the wavelength decreased.

The magnetic field distributions of overwritten patterns on rigid thin film disks were investigated using magnetic force scanning tunneling microscopy. The results showed that at high densities and offsets smaller than 2 micrometers, track width modulation was induced along the edges by overwritten transitions. These effects were less conspicuous at low densities.

Dynamic processes in 3380E and 3390 thin film heads at frequencies up to 200 MHz were investigated using quantitative analysis. The results showed that the phase lag of the longitudinal domain wall near the back gap of the 3380E head was a function of the drive field and it initially increased at a rate of 35 degrees per 10 MHz. When the phase lag reached between 35 to 45 degrees, the wall transferred to a new position where the phase lag was smaller. Damping limited head performance at frequencies above 50 MHz.

The characteristics of Gd1.6Bi1.4Fe3.8Ga1.2O12 garnet thin films were investigated for magneto-optical applications. The results showed that the thin films featured a high Faraday rotation, were resistive to corrosion and exhibited excellent magnetic characteristics. However, the sample had poor noise performance since the grain size was on the order of the recorded domain size. The films contained a high density of Bi globules which originated from the garnet matrix.

The CoCr phase of CoCr thin films was characterized using quantitative thermomagnetic analysis. A model in which magnetic exchange energy was the prime cause of phase separation was presented. The resulting CoCr phase diagram was in good agreement with the theoretical Hasebe model. In addition, calculations showed that the relative amounts of the different phases ranging from 40 to 55 vol % were nonmagnetic at room temperature.

The cause of wiggles in the read-back signal of a series of metal-in-gap heads has been studied. A Digitizing Signal Analyzer was used to analyse the read-back signals of the heads. These heads were then studied on a scanning magneto-optic photometer system by measuring the magnetic activity on the air-bearing surfaces. Defects having strong magnetic effects were observed in both the ferrite and the Sendust. It is shown that these defects are responsible for the wiggles in the read-back signal of these heads.

A series of FeN and FeAlN thin films were grown by reactive rf sputter deposition. Planar and cross-sectional specimens were investigated in the TEM. We observed that introduction of nitrogen is associated with improved magnetic properties and decreased grain size and that the introduction of Al is associated with improved thermal stability of both the magnetic properties and the microstructure. We also investigated the effect of lamination and the role of the interlayer. We found the best magnetic properties in annealed films with five 1000 angstrom thick FeN layers and four 25 angstrom thick SiO2 interlayers. High resolution TEM studies of cross-sectional specimens revealed an amorphous structure in this interlayer, providing crystallographic decoupling between the FeN layers. It is proposed that this SiO2 layer also serves to reduce magnetic exchange coupling between layers.

Correlation between noise-after-write and magnetization dynamics in 30-turn electroplated thin film heads has been investigated by utilizing two complementary magneto-optic Kerr effect domain imaging systems and a Barkhausen noise tester. It has been found that heads containing spike-like domains near the backgap closure have significantly higher noise-after-write rates than heads with normal closure domain configurations. A longitudinal 180 Degrees wall in the direction of flux conduction at the sloped region of the pole tip was observed, however, independent of whether the head had a high or low noise-after-write rate.