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The energy received by solar collectors for power generation is limited to various conditions. The average data on solar irradiation are normally used to determine the potential of solar energy at any location. However, the variation of solar energy due to seasonal differences could affect the actual performance of the collectors, consequently leading to poorly justified system installations, which are high in cost. In this work, the characteristics of solar energy radiation in Kuwait were studied by measuring irradiance and comparing the data of selected time periods in two extreme seasons. A pyranometer, mounted two meters above the ground on a tubular beam in a shade-free area at a solar energy laboratory in Kuwait was used to measure irradiance on three consecutive days in summer and winter. The radiation data were recorded at five-minute intervals in each season for comparison. It was found that the average irradiance energy in the winter was up to 61% less than in the summer. In addition, the study revealed that the day-to-day variation of irradiance in winter (31%) was approximately 6.5 times higher than in the summer (4.8%). Clearly, the operation of solar power generation systems in the area during winter would face significant day-to-day fluctuations. As a result, this would necessitate frequent operation of backup power systems in order to meet the electrical power load demand.

The effect of magnetic "preconditioning" on the recording performance of perpendicular media is investigated. Furthermore, the dependence of the magnetic write width (MWW) of shielded-pole heads (SPH) on soft-underlayer (SUL) type and thickness (t/sub SUL/) and the recording performance of perpendicular media with thin SULs are examined. The MWW dependence on SUL structure is influenced by the pole-to-trailing shield spacing. For a wide-gap (/spl sim/80 nm) SPH, thick single-layer, SULs are preferred. For a narrow-gap (/spl sim/50 nm) SPH, MWW is less sensitive to the SUL type. For both narrow and wide-gap SPH and for media with an antiferromagnetically-coupled SUL, MWW is reduced for t/sub SUL/

A recording density of 130 Gb/in/sup 2/ was achieved using thermally stable conventional CoCrPtB longitudinal media. The high in-plane orientation ratio (OR) of the media resulted in an excellent recording performance due to a narrow switching field distribution as well as a high thermal stability caused by narrow energy barrier distribution. The low noise is attributed to the fully isolated fine grains with a narrow size distribution. A good in-plane c axis crystallographic texture was achieved by using an optimum multilayered structure of underlayer and magnetic layers. A detailed study of high OR media is reported by characterizing the magnetic, microstructural, and read/write properties.

Magnetic patterns on perpendicular recording media were imaged by spin-stand level dynamic read-back microscopy. High-density tracks are clearly resolved up to 1000 kfci and details of magnetic bit structure, not usually observable using standard read-write tests, are readily observed. Encroachment of tracks on Co-Cr-Pt-O media with low oxygen content and low-coercivity results in a nonuniform erasure; as-written rectangular bits become trapezoidal in shape. Media with high oxygen content and high coercivity provide superior side erasure resistance

A systematic investigation of the structural and recording characteristics of CoPtCrO composite media with various Co alloys as well as continuous TbFeCo capping layers has been performed. For the media with a Co-alloy capping layer (M/sub s//spl sim/900 emu/cm/sup 3/), the transition jitter remains unaffected and dc noise is greatly reduced. However, for the media with low M/sub s/ capping layer or continuously exchange coupled TbFeCo capping layer, transition jitter is increased. Magnetically continuous but structurally discontinuous Co-alloy capping layers grown onto well-isolated Co grains can reduce dc noise, while maintaining low transition noise.

An anisotropy enhanced dual magnetic layer structure is proposed to improve the recording performance of perpendicular media. The initial layer is made of low noise Co-Cr-Pt-O layer and the top layer is made of higher anisotropy Co-Cr-Pt-B layer. A higher nucleation field than the single layer structures is obtained for the dual magnetic layer media. By optimizing the layer structure and properties, better signal-to-noise and lower adjacent track erasure can be achieved for the dual magnetic layer design over single magnetic layer media.

The permeability of the magnetic soft underlayer (SUL) was systematically varied through SUL structure change, and its effect on wide area adjacent track erasure (ATE) and media overwrite (OW) was studied. Results suggest that ATE decreases with SUL permeability, and it involves only a finite thickness of the SUL. OW increases with SUL permeability as well as SUL thickness. In addition, ATE is less affected by magnetic spacing than OW. Antiparallel coupled SUL (APS) improves ATE. A double-APS structure with a permeability gradient is proposed to optimize OW and ATE performance.

We discuss a method of ac-demagnetizing an entire disk using permanent magnets and compare the demagnetized states of perpendicular media with different levels of intergranular exchange. The method consists of applying a large field perpendicular to the media recording layer anisotropy direction. This bulk ac-erasure technique provides a background noise that is lower than that which can be achieved by ac-erasing with a write head. Highly exchange-coupled media exhibit low dc noise but increased ac-erased background noise. Magnetic force microscopy data show increased magnetic roughness in the ac-erased state with exchange-coupling strength. For the media with least coupling the dc noise is similar to the ac noise.

Compositionally graded magnetic multilayer (CGM) structures were investigated to improve media signal-to-noise ratio (SNR) as well as thermal stability. The medium structure consists of multiple magnetic layers that play an important role in determining the crystallographic texture as well as magnetic activation volume. Low medium noise is achieved while retaining high resolution, as the number of layers is increased. The CGM media offer a magnetic anisotropy gradient from the top to bottom layers, which enhances head writability at high frequencies without affecting thermal stability. Improved magnetic and recording properties such as high K/sub u/ V/kT, SNR, and overwrite are obtained with CGM media, suitable for high areal density recording.

A promising soft magnetic under layer (SUL) structure consisting of anti-parallel coupled soft layers (APS) is investigated to improve the performance of high-density perpendicular recording media. CoCrPt-O recording media with average grain diameter /spl sim/6 nm, coercivity of 5 kOe and nucleation field of -2 kOe is fabricated on both conventional SUL and APS. Wide-area adjacent track erasure (ATE) is observed for conventional SUL, which increases at lower interlayer spacing (t/sub IL/). APS structure enables the suppression of ATE even up to t/sub IL/=10 nm. Moreover, APS leads to reduced dc erase noise and improved signal to noise ratio particularly for SUL thicknesses

The effect of oxygen incorporation on the crystallographic, magnetic, and recording performance of perpendicular magnetic recording (PMR) oxide media was investigated. The media were prepared by dc-magnetron sputtering of CoCrPt-SiO/sub 2/ targets in an Ar/O/sub 2/ gas mixture. X-ray photoelectron spectroscopy (XPS) detected Cr-O peaks in the sputtered film, whereas no strong evidence of SiO/sub 2/ is seen. Moderate oxygen incorporation in the film (/spl sim/15 at%) promotes Cr-O formation in the grain boundary and results in a dramatic increase of coercivity H/sub c/ and signal-to-noise ratio (SNR). However, as the O/sub 2/ content is further increased, oxide incorporates into the core of the grains, resulting in decreased H/sub c/, magnetization and SNR.

Antiferromagnetically coupled (AFC) media and conventional media (CM) were compared side to side over a wide range of orientation ratios (OR). For both AFC and CM, oriented media outperform isotropic media. AFC and CM show similar signal-to-noise ratios (SNR) throughout the entire range of OR. CM exhibit good SNR performance even at M/sub r/t

Transition and DC noise characteristics of longitudinal recording media were studied as a function of orientation ratio (OR). With increasing OR, a substantial decrease of DC noise is observed against the gradually increasing transition noise, resulting in the reduced media total noise. The increase in the media transition noise with OR is attributed to the increase in the cross-track correlation length s. The experimentally estimated s for the media with OR=1.8 is significantly larger than that of the media with OR=1.25, possibly resulting from the difference in magnetostatically coupled Co grains aligned to the track direction. For high-density low M/sub r/t designs, reducing DC noise by increasing OR, in spite of an increase in transition noise, becomes an effective means to increasing areal density.

The structural, magnetic, and recording properties of longitudinal recording media with CrMoB underlayer were studied and compared to those with CrMo underlayer. Media with CrMoB underlayer have smaller grain size, better grain segregation, lower coercivity, and better recording performance than media with CrMo underlayer.

The recording performance of perpendicular media with amorphous CoZrNb, nanocrystalline NiFeNb, and exchange-pinned FeMn/NiFeNb soft magnetic underlayers (SULs) has been studied. A method has been proposed to quantify the spike noises from the SUL. We found that media with higher permeability NiFeNb SULs showed 4 db higher signal-to-noise ratio than media with lower permeability CoZrNb SULs. The exchange-pinned NiFeNb SUL suppresses spike noise and offers good recording performance. Furthermore, the recording frequency dependence of dynamic coercivity (Hc) was strongly affected by the use of different SULs. The increase in dynamic Hc with linear density is negligibly small for media with NiFeNb SULs, whereas dynamic Hc sharply increases with increasing density for media with CoZrNb SULs.

We have studied thermal stability and recording characteristics of CoCrPtB alloy media with varying c axis anisotropy dispersion, preferred orientation (PO), and in-plane orientation ratio (OR) on both glass and NiP-plated Al substrates. With increasing in-plane c axis orientation and OR, improved recording performances such as lower pulsewidth, lower media transition noise, and lower dc noise are achieved. Thermal decay rate is primarily determined by Co anisotropy dispersion and in-plane OR for the same coercivity media. Media having a large out-of-plane c axis component exhibit a wide switching field distribution and have a high signal decay rate. The PW/sub 50/ and dc noise of media with out-of-plane Co grains are very sensitive to changes in write field. On the other hand, highly oriented media having high OR are less sensitive to head writability variations and offer good thermal stability with excellent recording performance.

Summary form only given. Perpendicular magnetic recording (PMR) media has been considered as a promising candidate in order to achieve over 100 Gbir/in2 recording density. However, thermal stability at low recording densities has been a concern especially for low-noise PMR media. Achieving high perpendicular HC and unity squareness (SQ=Mr/Ms) is necessary to improve thermal stability and has been proposed by using either high substrate temperature or post annealing in CoCr based alloy. However, the influence of high heating on recording performance deserves further investigation. In this work, we studied on the seedlayer and heating effects on the crystallographic, magnetic and recording properties of CoCr18Pt16B4 granular PMR media. The CoCrPtB films were sputtered on preheated glass substrates with a Ru underlayer (UL) or a Ta/Ru UL on top of a 300-nm-thick NiFe17Mo4 soft magnetic underlayer. We report that Ta/Ru UL developed in this study greatly enhances Ru(0002)/Co(0002) crystallography, HC, SQ and thermal stability without degrading media signal-to-noise ratio (So/Nm).

The effect of magnetostriction (MS) on the device characteristics of soft-adjacent-layer (SAL) biased magnetoresistive (MR) head was investigated. As MS changes from -7/spl times/10/sup -7/ to 1.77/spl times/10/sup -6/, the magnetic track width increases from 1.26 to 1.83 /spl mu/m. Asymmetry of bias point, output sensitivity, and output amplitude are also affected by the stress induced anisotropy. The variation of magnetostriction (/spl Delta//spl lambda/=2/spl times/10/sup -6/) induces the change in bias field by 60 Oe associated with the estimated stress of +800 MPa on the MR stripe.

We report a simple, nondestructive B-H looper bending method for measuring 10/sup -7/ of magnetostriction (/spl lambda/) in thin films (/spl sim/150 /spl Aring/). The new method improves the accuracy and repeatability of /spl Delta/H/sub k/ measurements in loopers by employing a measurement sequence that corrects the non-repeatable balance errors. For the 150 /spl Aring/ thick NiFe films under an anisotropic strain of 4.6/spl times/10/sup -5/, we achieved a /spl Delta/H/sub k/ repeatability, 1/spl sigma/=0.009 Oe which is equivalent to 3.4/spl times/10/sup -8/ in /spl lambda/. Our technique gives /spl lambda/ values that agree well with the optical cantilever bending technique and can be easily utilized in a thin-film head production environment for accurate control of /spl lambda/.

The interface magnetostriction (MS), /spl lambda//sub i/ of NiFe films (thicknesses:50 to 500 /spl Aring/) encapsulated with Ta and Al/sub 2/O/sub 3/ layers was studied in as-deposited and thermally annealed states. The MS of NiFe films encapsulated with only Ta (or Al/sub 2/O/sub 3/) layers increase (or decrease) rapidly with decreasing NiFe thickness, due to giant positive (or negative) /spl lambda//sub i/. The magnitudes of both positive and negative /spl lambda//sub i/ increase noticeably with processing at elevated temperatures. In structures containing Ta/NiFe and NiFe/Al/sub 2/O/sub 3/ interfaces, the total interfacial MS contribution is greatly reduced due to the opposite signs of /spl lambda//sub i/ at NiFe interfaces, leading to negligible thickness dependence of the effective MS in as-deposited and annealed states. The strong interfacial MS induced anisotropy affects markedly the uniaxial anisotropy of NiFe films for thicknesses below 100 /spl Aring/.

FeMn based spin valves exhibiting high GMR ratio and high exchange bias field were fabricated by improving the interface roughness as well as the crystallographic texture. A highly oriented (111) NiFe free layer deposited with substrate bias promoted strong (111) textures of Cu and FeMn while maintaining sharp interfaces, resulting in a high exchange bias field, a high blocking temperature, and a high GMR ratio. The correlation between the interlayer coupling energy (J/sub free-pinned/) and the interface sharpness was studied as a function of Cu spacer thickness for spin valves with free and pinned NiFe layers deposited under various bias conditions.

This paper compares the images obtained by superparamagnetic and permanent magnetic force microscopy (MFM) tips, that allows us to explain the issues related to the frequency double in some of domain images of the recording media. This paper also investigates the domain structures of high density recording bits (up to 1100 kfci) written on ac and dc-erased CoPtCrO perpendicular magnetic recording (PMR) media with permanent magnet MFM tips under ambient conditions.

The effect of NiFe texture on the exchange coupling field and coercivity of Ta/NiFe/FeMn films was studied by varying the deposition conditions of dc magnetron-sputtered NiFe films. By decreasing argon pressure or by increasing substrate bias, strongly textured, large grains of NiFe(111) were grown, yielding highly oriented FeMn(111) texture. Well oriented NiFe(111)/FeMn(111) films yielded the highest exchange anisotropy (0.14 erg/cm/sup 2/), lowest coercivity (/spl ap/2 Oe), and highest blocking temperature (200/spl deg/C) ever reported.

Fe/sub x/Ge/sub 100-x/ films with compositions in the range 50/spl les/x/spl les/82 at 300 K were deposited by rf diode, sequential sputtering from elemental targets. All the films were amorphous at 300 K indicating that the Fe concentration in the stable amorphous films was increased by more than 10 at. % over that obtained by vapor deposition. The sequentially sputtered Fe-Ge films exhibited a heteroamorphous morphology with nanoscale features that varied with composition. The variations in the 4/spl pi/M/sub s/ and T/sub c/ for the sputtered Fe rich films, agreed well with data extrapolated from measurements on Ge rich evaporated films. The improvement in the soft magnetic properties produced in these films by rotating magnetic field annealing (RFA) was shown to be correlated with changes in film morphology.

Effect of Co grain morphology on Cr segregation induced magnetic properties was investigated in heat treated CoCrPt/Cr thin films. In this work, interdiffusion and Cr segregation induced Co grain isolation were studied by post-deposition annealing of the CoCrPt films deposited on a Cr underlayer at different sputtering conditions. The films with voided boundaries showed a stronger heating temperature dependence of magnetic properties than the dense films, due to the promoted Cr segregation at the boundaries. TEM observation indicated that Cr was segregated from the Cr underlayer to the void boundaries of the CoCrPt films. The grain morphology of as-deposited films played an important role in Cr segregation during heat treatment, and the intergranular exchange decoupling was enhanced by the diffusion of Cr atoms into the voids isolating the Co grains.

A highly sensitive optical interferometer with in-situ calibration was developed to measure the low-field magnetostriction of magnetic thin films using the cantilever beam technique, The high displacement resolution (0.01 /spl Aring/) of this instrument permits the measurement of magnetostrictions of 10/sup -9/. First measurements on a soft CoFeSiB thin film were made to demonstrate this technique. The magnetostriction measurement resolution of 5/spl times/10 obtained is the lowest yet reported value. The dynamic range of the technique was demonstrated in measurements of a magnetostriction greater than 10/sup -5/.

Amorphous wires and ribbons of composition Co/sub 70.5/Fe/sub 4.5/Si/sub 15/B/sub 10/ have a very small magnetostriction and very low coercivities for wall motion. Their high permeabilities are of considerable technological interest. Thin films of these alloys might be useful for applications, but had not been previously studied. This work studied the structural and magnetic properties of amorphous thin films sputtered from an alloy target with the composition Co/sub 70.5/Fe/sub 4.5/Si/sub 15/B/sub 10/. The results obtained show that the coercivity and in-plane anisotropy of the sputtered films are much larger than those of ribbons and wires. Attempts to reduce these parameters by varying the processing and annealing parameters, substrate material, composition, and film thickness were largely unsuccessful. While these results are not understood, the composite data suggests that the higher values may be due to micro-compositional inhomogeneities resulting from higher effective quench rates of sputtering.

Exchange-shifted hysteresis loops were observed at 300 K in thin amorphous films deposited from a CoFeSiB alloy target by reactive oxygen sputtering. The heterogeneous film morphologies consisted of nanoscale features with thin, apparently oxidized, boundaries, The exchange shift varied with the film thickness, and with the ratio of the oxygen to argon gas flow, The CoFeSiB:O films exhibiting exchange anisotropy had resistivities in the range /spl sim/10/sup 3/ /spl mu//spl Omega//spl middot/cm to /spl sim/10/sup 4/ /spl mu//spl Omega//spl middot/cm. The maximum shift (/spl sim/10 Oe) was observed in films with a resistivity of /spl sim/2500 /spl mu//spl Omega//spl middot/cm. The exchange anisotropy appears to be due to coupling between nanoscale regions with different coercivities.

Summary: Spinal intradural extramedullary capillary hemangiomas are extremely rare. We present the MR imaging and histologic findings in three patients with this abnormality. The three patients were men who had symptoms of either myelopathy (n = 2) or radiculopathy (n = 1). The tumors were well demarcated, 1.5–2.0 cm in diameter, and were located at the posterior or posterolateral portion of the thecal sac (one at the L1 level and the other two at the midthoracic level). On MR images, the tumor showed isointensity relative to the spinal cord on T1-weighted images, hyperintensity on T2-weighted images, and strong homogeneous enhancement on contrast-enhanced T1-weighted images in all three patients. In two patients, the dural tail sign was observed. Capillary hemangioma should be included in the differential diagnosis of a spinal intradural extramedullary tumor.

Summary: Clear-cell meningioma is a rare disease entity showing a more aggressive nature, clinically, than those of other subtypes of meningioma. It occurs in younger persons and commonly in the spinal canal. The recurrence rate has been reported to be as high as 60%. We present a case of clear-cell meningioma in a 17-year-old man in whom initial MR imaging showed localized leptomeningeal enhancement that had progressed into the entire subarachnoid space after surgical resection of the primary tumor.

Systemic sclerosis (SSc) is a polygenic, autoimmune disorder of unknown etiology, characterized by the excessive accumulation of extracellular matrix (ECM) proteins, vascular alterations, and autoantibodies. The tight skin (Tsk)2/+ mouse model of SSc demonstrates signs similar to SSc including tight skin and excessive deposition of dermal ECM proteins. By linkage analysis, we mapped the Tsk2 gene mutation to