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A dc magnetron co-sputtering system incorporating a rotating substrate table has been used to produce Dy-FeCo films with a multilayered structure. For this study a series of films were produced in which the periodicity was varied whilst the overall composition and film thickness were kept constant. The magnetic, thermo-magnetic and magneto-optic properties of the films have been measured in an attempt to establish the best layer structure and periodicity for good thermo-magnetic recording characteristics. For the two compositions studied, Dy22Fe68.5Co9.5 and Dy28Fe52Co20, the optimum characteristics were found for films in which the rare earth Dy layer is approximately one atomic layer thick.

The optimisation of magneto-optical data storage disk structures requires a knowledge of the optical and magneto-optical constants of the storage material. In this paper we present the optical (n + ik) and first order magneto-optical (Q1 + iQ2) constants for the rare earth-transition metal alloys: Tb23.5Fe72.5Co4.5, (Tb23.5Fe72.5Co4.5)89Pr11, Dy22Fe68.5Co9.5 and Dy28Fe52Co20. A combination of Kerr polarimetry and ellipsometry is used to evaluate these constants, which are then used to calculate the magneto-optic response as a function of magnetic layer thickness. A comparison between calculated and measured Kerr responses from both the air and substrate side of these structures reveals the self consistency of the modelling process and the validity of the determined constants.

Amorphous TbFeCo films have been manufactured with a rotating substrate, multi-target, dc magnetron cosputtering process. The light rare earth praseodymium (Pr) has been doped into these TbFeCo alloys in an attempt to increase the intrinsic polar Kerr rotation. Magneto-optical measurements however, indicate a degradation of the Kerr rotation with Pr content in the new alloys. The deterioration of the magnetic properties, the coercivity, the squareness of the hysteresis loop shape and the perpendicular anisotropy are also shown to be a result of Pr substitution.

The optical constants of a magnetic material may be determined by simultaneous measurement of the fractional changes in both the reflectance and the absorption introduced in the magneto-optic interaction when the sample magnetisation is reversed between saturated states. The magnetisation dependent photometric parameters, R and A, are determined without absolute measurement of optical intensity.

Magneto-optical measurements of the anisotropy of homogeneous Dy/sub 18/Fe/sub 82/ films as a function of thickness (134.0-13.4 nm) confirm that the perpendicular anisotropy disappears when films are less than 60 nm thick. Since, the range of films exhibits both out of plane and in-plane anisotropy, both the polar Kerr effect and the transverse Kerr effect were used to determine the anisotropy. At about 60 nm the perpendicular anisotropy K/sub /spl perp///spl les/ the shape anisotropy (K/sub s/=2/spl pi/M/sub s//sup 2/).

Comparison is made between the experimental and theoretical behaviour of the magneto-optical properties of a series of Co-SiO/sub 2/ films in which the volume fraction q occupied by the particles is varied between 0.4 and 0.8. A modified Maxwell Garnett model is used to compensate for both the surface oxidation of the cobalt particles and the reduced electron mean free path.

Granular cobalt films about 500 nm thick and ranging in composition from 0.25-0.85 fraction by volume of cobalt have been prepared by co-sputtering cobalt and silicon dioxide from a mosaic target. At a given sputtering power and pressure the volume fraction (q) of cobalt in the films is determined by the areal fraction of the SiO/sub 2/ base target covered by the cobalt mosaic. Transmission electron microscopy indicates that the samples are composed of particles of cobalt with diameters in the range 2.5 nm-6.5 nm dispersed in the SiO/sub 2/ matrix. Magnetic properties of samples with q in the range 0.25-0.85 are measured using a vibrating sample magnetometer. Samples with q below 0.52 are generally superparamagnetic in their as-deposited state. Subsequent rapid thermal processing (RTP) is shown to initiate ferromagnetic behaviour with a coercivity that increases with processing temperature. Optical constants of the films, measured by ellipsometry, are found to be in good agreement with Maxwell Garnett theory. Some films exhibit a saturation polar Kerr rotation that is significantly greater than that of pore cobalt films.

Magnetic properties of critical importance to the thermo-magnetic recording process are shown to be structure dependent. The use of structure as an additional tool in the control of these properties is illustrated by experiments that compare the size of domains written thermo-magnetically into different structured DyFeCo films. Samples with a common average composition and all 40 nm thick and with form that varies from the conventional homogeneous amorphous alloy to a material consisting of discrete Dy and FeCo layers, have been investigated. It is found that, whilst the Curie temperature, compensation temperature and saturation magnetization reflect the consistency of the average composition and remain constant across the range, the perpendicular anisotropy and coercivity are structure dependent and increase as the films become more layered, reaching a maximum when the rare earth (RE) layers are nominally one monolayer thick. In the writing experiments this behaviour is observed as the creation of different sized stable domains under constant write conditions.

The magnetic and structural properties of BaFe/sub 12/O/sub 19/ films prepared by sputtering are compared with samples deposited using laser ablation deposition (LAD). Both techniques yield as-deposited films that are without crystal structure and consequently non-magnetic. The development of crystal structure and associated magnetic properties after rapid thermal processing (RTP [1]) and ultra-rapid thermal processing using a CO/sub 2/ laser is presented. Early results indicate that control of the oxygen content of the material is of critical importance during both preparation and subsequent processing. Provided this control is present a material with a significant perpendicular magnetic anisotropy can result from very rapid thermal processing. >

The original concept for digital optical memory envisaged a random access, beam addressable system. However, to facilitate the rapid development of write-once (WORM) and rewritable thermo-magneto-optic optical storage products, it was expedient to adopt the rotating disk format together with the servo control and access systems that had already been brought to a high level of refinement by the magnetic recording industry. Whilst the performance of present disk servo systems is undoubtably impressive, there must inevitably come a time, as processor speeds continue to increase and electronic processors are superseded by optical equivalents, when mechanical servo systems severely limit the ultimate performance of a data processing system. To address this issue we have considered some of the problems inherent in beam addressed systems by investigating the use of media developed for the current generation of disk based WORM and MO recording systems in a beam addressable format.

A rapid thermal annealing (RTA) process has been developed that permits the preparation of well ordered films of barium ferrite (BaFe/sub 12/O/sub 19/) in minutes, rather than the hours conventionally required. Optical fluxes approximately=40 W cm/sup -2/ are used to produce linear heating rates up to 20 degrees C sec/sup -1/ and achieve final sample temperatures in excess of 750 degrees C in less than one minute. Frequency and duty cycle modulation of the radiant optical energy allows close control of the heating cycle and the production of different RTA regimes. The magnetic and structural properties of the annealed samples have been shown to be dependent on the particular regime followed. >

The structural characteristics and the experimentally measured optical constants (n and k) and magnetooptical constants (Q/sub 1/ and Q/sub 2/) for RF-sputtered Mn/sub x/Sb/sub 1-x/ films are reported for x in the range 0.13 >

The optical and magneto-optical properties of thin films of the Heusler alloy PtMnSb have been studied as a function of the wavelength of the incident radiation. The optical constants n and k , presented for as-deposited and annealed films, show significant variations as a result of the annealing process.

A model for the magneto-optic properties of ferromagnetic cylinders in a dielectric matrix is applied to anodized aluminum films, consisting of cobalt filled micropores in an alumina matrix, which have potential for magneto-optic applications.

A study of the effect of substrate character and morphology on the magnetic and magneto-optic properties of rf sputtered Mn (13–83 at%)Sb films indicates a marked effect on the development of in-plane coercivity.

A technique is reported for accessing the absorptive component of magneto-optic interactions. Photo-acoustic detection is used to record hysteresis loops more usually obtained by monitoring changes in the reflectivity of samples as the magnetization is reversed. The sensitivity of the technique and its application is discussed.

A simple, versatile system has been developed for the production of ordered magneto-optic thin films by rapid thermal annealing (RTA). The system is capable of sample heating rates of between 10 and 20°C per second and final temperatures in excess of 800°C in less than a minute. Details of the system are provided together with the results obtained with sputtered films of PtMnSb. The structural, magnetic, optical and magneto-optical characteristics of the annealed samples are compared with those obtained using a conventional annealing system.

Optical constants have been measured for sputtered thin films of platinum, cobalt and multilayer Pt/Co. Magneto-optical constants have also been measured for the films containing cobalt. These constants are presented as a function of the thickness of the films and the wavelength of the incident radiation. The relevance of these measured constants to the optimisation of disk structures is considered.

The advantages, difficulties and limitations of photometric techniques for the determination of optical constants are discussed. An optimized self-consistent procedure is used to evaluate the optical constants of a series of cobalt films from simple relative reflectance measurements. The films are polycrystalline and range in thickness from 110 to 10 nm. In addition to possible interband structure a strong resonance peak was observed in their optical absorption spectrum at 1.1 eV. This is tentatively identified as “optical conduction resonance” which is a collective free-electron oscillation in the aggregated surface or structure of the films.

Experimentally measured magneto-optical properties of magnetic materials are usually analysed using a phenomenological approach in which the permittivity is considered as a skew-symmetric tensor. Measurements of the real and imaginary parts of both the optical and the magneto-optical elements of this sensor in the region 1.0–2.5 eV are presented for a series of seven thin (108-13.4 nm) cobalt films. The prominent features of the results are remarkably consistent from film to film.

Using a general scattering matrix approach in the theoretical analysis the polar Kerr rotation is shown to have a marked dependence on sample thickness when the thickness is less than 60 nm. The polar Kerr rotation is calculated for thin films of iron and cobalt for normal incidence in the wavelength range 400–1400 nm for both unbloomed and bloomed specimens.

The polar Kerr rotation developed by thin films of granular material is calculated for spherical cobalt particles in an SiO2 insulator matrix. Effective optical and magneto-optic parameters are calculated for different volume fractions q of particles with radii in the range 1.5–6.0 nm. Films of dispersed particles with radius 4.5 nm are shown to produce polar Kerr rotations approximately two times greater than those for continuous films of the same thickness. The potential of such films as a thermomagnetic recording medium for data storage is briefly discussed.

The transverse Kerr effect was measured for thin cobalt films (of thickness 13–108 nm) at three angles of incidence over the visible and near infrared wavelength range. A new technique is introduced for the evaluation of the magneto-optic constants Q1 and Q2 (Q = Q1+iQ2) by using these measurements together with previously determined optical constants. Both Q1 and Q2 are found to be thickness dependent. For a fixed thickness, Q1 is found to be fairly uniform over the wavelength range considered but a marked resonance occurs in Q2 at approximately 1.1 eV.

Thin films of Nd-Fe prepared by rf sputtering are shown to exhibit marked perpendicular anisotropy. Hysteresis loops with a sqaureness ratio of essentially 1.0 with large coercivities and significant polar Kerr rotations are reported for films with 60 at% Nd.

Etude par effet Kerr polaire de couches minces de Nd−Fe avec une concentration en Nd d'environ 60% at. preparees par pulverisation en haute frequence

Le retournement de l'aimantation dans plusieurs couches minces Gd-Co de composition entre 20 et 46% Gd, deposees par pulverisation r.f., a ete etudie par effet Kerr polaire a λ=633 mm, sous des champs jusqu'a ±10 kOe. Le trace de la coercivite en fonction de la composition met en evidence des maxima tres marques qui sont attribues a des transitions du sous reseau magnetique dominant dans le film, et semblent se manifester par des maxima dans l'aimantation a saturation

Valeurs mesurees des constantes magnetooptiques pour Co 1−x Cr x avec 5≤x≤27% at. pour des longueurs d'onde de 497 a 1250 mm

In clinical practice it is a frequent requirement to identify disease rapidly and more importantly to establish the onset and course of malignant disease. It is towards this end that many new diagnostic techniques are sought. Some techniques have been developed that rely on the examination and analysis of blood and more recently laser techniques have been developed to sort and measure blood samples.© (1983) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

It has been assumed that GdCo only possesses the properties necessary to support perpendicular thermomagnetic recording at or close to the magnetic compensation composition. We have recently discovered at least two other compositions which exhibit both the perpendicular anisotropy and the temperature dependent coercivity required of a storage medium.