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We measured longitudinal and transverse magnetooptic Kerr effect loops to understand the angular dependence of magnetization reversal in an array of 5 [micro]m x 25 [micro]m rectangular thin Co bars with uniaxial anisotropy. When the magnetic field is applied close to the hard axis, the reversal is dominated by coherent rotation; when the field is applied close to the easy axis, the reversal is caused by domain-wall unpinning and the coercive fields observe the relation [H.sub.c] = [H.sub.0]/cos [[theta].sub.0] For the other orientations, the magnetization first rotates smoothly at larger fields and then switches irreversibly by domain-wall unpinning. Index Terms--Coherent rotation, domain-wall nucleation, domain-wall unpinning, magnetization reversal.

Analytical representations of Jones matrices for the magneto-optic (MO) reflection in (a) a magnetic film on a magnetic substrate separated by a nonmagnetic spacer and (b) two ultrathin magnetic films separated by a nonmagnetic spacer, sandwiched between a nonmagnetic cover and a nonmagnetic substrate with arbitrary and independent orientations of magnetization, are provided. Originally isotropic media subjected to a uniform magnetization are considered. The discussion of MO response is restricted to the terms linear in the off-diagonal permittivity tensor elements, and typical situations are illustrated numerically. The results are useful for the analysis of the experiments in MO ellipsometry and MO magnetometry of exchange-coupled magnetic ultrathin-film structures. OCIS codes: 240.0310, 210.3810, 260.2130.

This paper presents a novel technique for integrating yttrium iron garnets, namely Ce :YIG, onto semiconductor platforms using metal-organic chemical vapor deposition (MOCVD). Large amounts of cerium (Ce) could be incorporated into the garnet structure because of the nonequilibrium nature of the technique. The method can alloy up to 54 % Ce, thereby increasing the refractive index and enhancing the Faraday rotation of the YIG films. Faraday rotations as high as 0.4 [degrees] / [micro]m at 1.3 [micro]m were achieved in MOCVD-grown garnets, exceeding the rotations of bismuth-doped YIG films (0.15 [degrees] / [micro]m at 1.3 [micro]m) grown by liquid-phase epitaxy. The easy axis of magnetization is within the plane of the films. When the garnet films were sputtered onto (100) magnesia (MgO) buffer layers, their hysteresis loops indicated that they were isotropic. Index Terms--Ce, Faraday rotator, garnet, magneto-optic.

Digital information in optical data storage systems can be encoded in the intensity, in the polarization state, or in the phase of a carrier laser beam. Intensity modulation is achieved at the surface of the storage medium either through destructive interference from surface-relief features (e.g., CD or DVD pits) or through reflectivity variations (e.g., alteration of optical constants of phase-change media). Magneto-optical materials make use of the polar magneto-optical Kerr effect to produce polarization modulations of the focused beam reflected from the storage medium. Both surface-relief structures and material-property variations can create, at the exit pupil of the objective lens of the optical pickup, a phase modulation (this, in addition to any intensity or polarization modulation or both). Current optical data storage systems do not make use of this phase information, whose recovery could potentially increase the strength of the readout signal. We show how all three mechanisms can be exploited in a scanning optical microscope to reconstruct the recorded (or embedded) data patterns on various types of optical disk. OCIS codes: 210.0210, 350.5030, 120.3180, 170.5810.

The preparation of amorphous thin films of DyFe100-x and Dy20Fe80-yCoy using sputtering on polyimide films is described and their magnetic and magneto-optical properties are presented.

Research into the magnetic properties of nanoarrays is presented. It was established that Brillouin scattering, magneto-optical Kerr effect and diffracted-magneto-optical Kerr effect methods give powerful and useful tools with which to identify the features of magnetic nanoarrays.

Issues concerning the flux penetration of current induced external magnetic fields of YBCO-thin films to determine inhomogeneities in large areas. Magnetic interactions between YBCO-bridges and current directions are detailed.

The giant magneto-impedance effect in magnetic microwires is examined.

Magnetoresistance measurements were used to study magnetization reversal in permalloy wire junction structures.

A new study investigates the magneto-optical properties of Co-Pt alloy films at low and ambient temperatures.

Results of numerical computations pertaining to evanescent wave coupling for near-field magneto-optical and phase-change disks based on the concept of the solid immersion lens are presented. We investigated the relation between the coupling efficiency and the width of the air gap in terms of the throughput of the recording process and the resolution of the readout signal. The simulations show a drastic decrease with a widening air gap of the coupling efficiency by means of evanescent waves into the recording medium. In magneto-optical readout, loss of the signal may be attributed to the reduction of magneto-optical interaction, the rise of reflectance, and the variation of the relative phase between the two components of polarization. In the phase-change readout the reduced refiectivity contrast between crystalline and amorphous marks is the cause of signal reduction.

The nonreciprocal effect is the difference (delta)(beta) = (beta)forward - (beta)backward between forward and backward-propagation constants of optical modes. This effect is analyzed for the fundamental TM(sub oo) mode of channel waveguides in epitaxially grown magnetic garnet films. To increase /(delta)(beta)/, double layers with opposite signs of Faraday rotation are used to prepare the waveguides. It is shown that the temperature dependence of (delta)(beta) can be reduced considerably if the layer with positive Faraday rotation, which is at room temperature close to the Curie point, is replaced by a paramagnetic layer with negligible Faraday rotation. Concurrently, however, /(delta)(beta)/ is decreased by approximately 35% at 295 K.

Research was conducted to examine two kinds of trilayer structures, namely Pt/Co/Pt grown on Al2O3(0001) monocrystalline substrate and Pt/Co/Au deposited on float glass. Spectroscopic magneto-optic Kerr rotation experiments were performed on Pt/Co interfaces. Results demonstrate drastic change in the 400-500 degrees C temperature range with a strong increase of the interface anisotropy and of the saturated magneto-optical Kerr rotation near 350 microns.

Magneto-optical methods were applied for the first time in millimeter wavelength range for characterization of anisotropic ferrites. The principles of the free-space magneto-optical method are presented and the new experimental procedures leading to the determination of millimeter-wave permeability and permitivity in anisotropic ferrite materials are described. The measurements were performed with a computer-controlled W-band (70-120 GHz) quasi-optical-waveguide bridge. A backward-wave oscillator was used as a source of tunable millimeter wave radiation. The oriented Sr-hexaferrite ceramic was selected for the verification of millimeter-wave magneto-optical method. The magneto-optical measurements in transverse configuration revealed strong anomalous dispersion in the millimeter-wave refractive index spectrum for Sr hexaferrite, mainly due to the frequency variation of magnetic permeability. Computer simulations revealed a good agreement of measured parameters with known data for Sr hexaferrite. It was shown that the free-carrier absorption ([Sigma] [similar to] 0.0. [[Omega].sup.-1] [cm.sup.-1]) and magnetic permeability contribute to the relatively high millimeter-wave losses in hexaferrite ceramics. The frequency dependence of Faraday rotation in the millimeter-wave range was measured, and the experimental results are discussed. The results presented in this paper demonstrate that this new magneto-optical method is capable of providing accurate dielectric and magnetic data in the millimeter-wavelength range. Index Terms - Anisotropy, hard ferrites, hexaferrites, magnetic permeability, magneto-optics, millimeter waves.

A study was conducted to analyze different crystallization states of melt-spun Co80B20 alloys. Transmission electron microscopy, high-resolution transmission electron microscopy and magneto-optical Kerr effect were utilized to carry out the analysis. Experimental results indicated that the volume fraction and median grain size of the Co3B decreases during increases in the annealing temperature.

A magneto-optical method, conceived in our laboratory to measure Brown's relaxation frequency of ferrofluids, is compared with Fannin's technique based on impedance measurements (slit toroid). We have developed a complete theory and an experimental setup of the first method and have briefly described the second one. We present a study of Brown's relaxation of cobalt ferrite [Fe.sub.2]Co[O.sub.4] in different carrier liquids (glycerol, diethylene glycol, dibutyl phthalate, and water). The two methods show very close results, proving the high sensitivity of both. The relation between the viscosity [Eta] and Brown's relaxation frequency [f.sub.B] has been verified. Moreover the analysis of relaxation and viscosity versus temperature has enabled us to estimate the hydrodynamic diameter of particles. Index Terms - Magnetic liquids, magnetic relaxation, magnetooptic effects, permeability, viscosity.

A study was conducted to analyze the impact of depositing submonolayer quantities of copper onto the carbon monoxide-exposed Co/Cu(110) system using the magneto-optic Kerr effect. The copper overlayers reversed the in-plane 90 degree easy axis switch caused by the carbon monoxide adsorption. Experimental results indicated the stabilization of ferromagnetic order by magnetic anisotropy in an ultrathin magnetic film.

The extended Jones matrix method is applied for determination of the transmission and reflection matrices for a normally incident plane wave upon an homogeneous and lossless biaxial thin layer. The elements of these matrices ace expressed by simple analytical relations. By using these relations one can express analytically the polarization-dependent optical parameters to be determined by generalized ellipsometry.

Highly accurate optical magnetic-field probe sensors that use iron garnet films have been developed. New probe-type sensors were designed with a confocal optical system. A new garnet composition, [Bio.sub.0.98][Gd.sub.0.92][La.sub.0.03][Y.sub.1.07][Fe.sub.4.72][Ga.sub.0.28][O.sub.12], was found that shows high temperature stability for a sensitivity of less than 2.0% from -20 to +80 [degrees] C. The linearity error of the sensor output was within 1.0% for alternating magnetic fields from 0.3 to 42 mT. An optical current transformer that uses the proposed sensor has an ac linearity of 1.0% for input current up to nearly 300 A. The sensor realized high performance in actual use.

A chemical sol-gel method was utilized to synthesize rare earth doped CoFe2O4 nanocrystalline films. The films were composed of nanometer grains with the spinel structure. Rare earth doped cobalt spinel ferrites were found to have alterations in magnetic and magneto-optical (MO) properties, with increases in their coercive force and enhancement of the MO rotation in the Tb(supra 3+) doped sample.

A study was conducted to analyze nonreciprocal phase shift for TE modes in magnetooptic rib waveguides supporting a compensation wall. Perturbation theory was utilized to compute the nonreciprocal phase shift. The electromagnetic fields were then obtained using a semivectorial finite-element technique. Results indicated that the maximum nonreciprocal phase shift can be improved by a factor of 1.3 up to 1.8.

The behavior of the interlayer coupling, optical and magneto-optical Kerr effect in nickel80cobalt20/copper multilayers was investigated. A series of radio frequency sputtered NiCo/Cu multilayers was prepared for the experiment. It was found that a concurrent oscillation in the magnitude of the magneto-optical Kerr effect and giant magnetoresistance effect exists as a function of copper thickness. The findings suggest that the antiferromagnetic coupling may alter both the optical and magneto-optical transitions and produce additional magneto-optical Kerr effect.

The nature of the magneto-optic Kerr effect in a planar dielectric waveguide geometry has been investigated by calculation of the Jones matrix for a planar waveguide structure with a gyrotropic magnetic material as one wall. The intensity of the component of the field that is in the polarization state orthogonal to the input was calculated as a function of length of the gyrotropic material and input polarization state. The degree of polarization rotation depends on the relative orientation of the magnetization in the magnetic material and the direction of propagation. It is found that there exists an optimal waveguide length and input polarization at which the output signal is maximized and that a significant enhancement in polarization rotation is available with respect to free-space reflection. These results indicate that a magnetic-film-bounded planar waveguide can be used for device applications such as magnetic field sensors or magneto-optic modulators.

An experimental demonstration of a noninvasive optical probe of magnetic fields is presented. The technique used is magnetic rotation spectroscopy of the [Mathematical Expression Omitted] band of oxygen near 760 nm. Ambient concentrations of oxygen at atmospheric pressure are sufficient to observe substantial signals. In addition, a diode laser is used as the light source, making this a simple and compact measurement possibility.

A homogeneous ferrofluid composition capable of reversibly forming ordered crystalline two-dimensional hexagonal lattices of magnetic particle columns in a thin film under the influence of external magnetic fields has been synthesized. We can manipulate the spacings between the particles columns by adjusting parameters such as external magnetic field strength, film thickness, rate of change of the field strength, and concentration of magnetic particles in the ferrofluid. These spacings between particle columns are of the order of several micrometers and are capable of diffracting visible light to produce monochromatic interference colors. We can change the resulting colors by altering the lattice spacing to exhibit the feasibility of generating monochromatic colors.

A study was conducted to examine the effects of copper (Cu) dopped into platinum (Pt) spacer layers on magneto-optical features for sputtered Pt/Co multilayers. Multilayers were deposited on a water-cooled glass substrate by magnetron sputtering and Ar gas at 7.5 mTorr while the Cu content in the Pt layer was measured using an inductively coupled plasma-atomic emission spectrometry system. Results suggested that oscillation behaviors may be correlated with the spin polarization in PtCu layers.

High-density magneto-optical recording using near field optics with a solid immersion lens is discussed. The spot size, and defocusing distance are calculated for various combinations of n and NA. Also, the misalignment of the objective lens and SIL is discussed, The magnetic and magneto-optical properties of SIL media candidates of TbFeCo/Pt multilayers are presented.

A study was conducted on the structural and spectroscopic magneto-optics of Pt-Ni multilayers. The results indicate that Pt-Ni compositionally modulated multilayers grown by e-gun evaporation under UHV conditions present satisfactory modulation with composition profiles similar to those of the ideal rectangular wave one. An unexpected development of perpendicular anisotropy was also observed through magneto-optic measurements at room temperature.

RF sputtering was used in preparing hexaferrite thin films of Ba1-xRxFe12-xNixO19 on nonmagnetic garnet substrates. Crystallization with the c axis oriented towards the film plane was observed after deposition at 550-degrees C substrate temperature. Transmission electron microscopy shows that low rf power density-deposited films contained nm-size microcrystallites locally.

Exchange-coupled rare-earth transition-metal triple layer stacks and discussed relative to wall energy and wall thickness. Less wall energy was the result of a different wall structure vs perpendicular layers. With knowledge of exchange stiffness and uniaxial anisotropy wall energy and thickness were calculated. Excellent agreement with magnetic measurements was seen.

Epitaxial films of Y3-xPrxFe5O12 have been grown on (111)-oriented Gd3Ga5O12 (GGG) substrates using rf sputtering methods. The Pr substitution induces negative Faraday rotation and ellipticity with a paramagnetic dispersion relation caused by an electronic transition centered at 3.0 eV. Pr contribution is -2.5x10(super)4 degrees per centimeter in rotation and -4.1x10(super)4 degrees per centimeter in ellipticity for x=2.0.

A solid immersion lens attached to a conventional objective increases the effective numerical aperture (N[A.sub.eff]) of an optical pickup and yields an areal recording density proportional to [(N[A.sub.eff]).sup.2]. One version of this device, with an effective (N[A.sub.eff]) of 1.7, should be capable of very high density storage but would probably need a sealed system. Another simple configuration enables the use of this method for optical data storage in an unsealed environment and extends the spatial cutoff frequency 1.5 times. Experiments with these devices are compared with the full vector field theory of this type of imaging system. Key words: Solid immersion lens, vector field theory, near-field recording, magneto-optical disk.

The behavior of a Faraday-active turbid medium under ultrafast optical excitation is investigated. As the degree of polarization of early arriving photons is mostly preserved during the first 100 ps after the arrival of the ballistic component, the possibility of using the magneto-optical rotation of the light polarization as a new tool for tissue characterization is addressed. A technique is proposed for determining photon-scattering statistics in turbid biological media. The analysis is performed on the basis that photons trapped in multiple-scattering events leave the medium with larger induced rotation angles. A measurement of the magneto-optical rotatory power of turbid biological samples is possible if only the early arriving unscattered photons are probed.

Magneto-optical images of YBa2Cu3O7-delta samples in the force-free configuration of a magnetic field are investigated. Several vortex lines were observed to twist together to form very stable structures. Some of the 'vortex twisters' were even observed to interact to generate wave-like dynamics. Data suggest that the thermodynamic phases of entangled vortices are inherently stable and may occupy a large part of the mixed-state phase diagram for type-II superconductors.

In this paper, we present the results of an investigation into the temperature dependence of fluctuation fields, activation volumes, and coercivity in Tb-Fe-Co magneto-optic thin films. Using the model of domain wall dynamics developed by Gaunt, both the temperature dependence of the intrinsic energy barrier distribution and the domain wall pinning regime are examined. The results show that at elevated temperatures, the intrinsic energy barrier distribution changes in a way that assists magnetization reversal, leading to greater activation volumes as the magneto-optic write temperature is approached. Analysis of coercivity as a function of temperature shows that these magneto-optic thin films are subject to a strong domain wall pinning regime.

The Faraday rotation and infrared studies of ([Y.sub.3-y][Ce.sub.y]) [(Fe, Ga).sub.5][O.sub.12] (Ce = 0 to 20% relative metal content) garnet films deposited on quartz and [Gd.sub.3][Ga.sub.5][O.sub.12] (GGG) are reported. The value of [[Theta].sub.f] reaches a maximum with Ce between 5 and 15%, depending on the heat pulse annealing temperature. The film crystallinity deposited on quartz, analyzed by X-ray diffraction and by sharpening of bands near 500 [cm.sup.-1] in FTIR, reaches a maximum with Ce = 5% and then decreases. Values of the Faraday rotation are related to the crystallinity of the deposited films.

The optical transition coefficient of two electrons confined in a pair of coupled quantum dots under a magnetic field was computed. The applied magnetic field causes substantial modifications in the optical-transition coefficients and induces new kinds of optical transition. However, when the distance is large, the Mott insulating states of a pair of electrons are less sensitive to an external magnetic field because of the small size of each quantum dot.

We captured Rb atoms in a magneto-optic trap by using two frequencies in an injection-seeding process of a diode laser without the use of a separate repumping laser. In the incomplete injection-seeding condition, the power of the free-running slave laser at the repumping frequency can be partially converted into power at the master laser frequency, which is stabilized at the cooling frequency. We measured conversion efficiencies and frequency shifts based on the injecting power and the preset frequency difference between the master laser and the slave laser.