Using rapid thermal processing (RTP) we recently demonstrated the production of high quality well ordered barium ferrite films in times much shorter than those required by a conventional annealing process. Influence over the magnetic and structural properties developed in annealed samples was also achieved by variation of the RTP heating profile (R. Carey, P. A. Gago-Sandoval, D. M. Newman, and B. W. J. Thomas, presented at Intermag-93, Stockholm, April 13–16, 1993). It is known that the magneto-optic properties of barium ferrite can be enhanced by selective substitution of some of the Fe by Co2+ and Ti4+ albeit at the expense of reducing the magnetic anisotropy. A multitarget scanning cosputtering process has been used in conjunction with rapid thermal processing to produce a series of barium ferrite films in which Co, Cr, Mn, Ni are selectively introduced to substitute for between 5 and 20 at. % of the Fe. A corresponding percentage of Ti is also added to maintain charge compensation. The magnetic and magneto-optic properties of these films are presented and discussed with reference to their composition and treatment respect to the properties of barium ferrite.

We have investigated the effects of the particle size distribution on the giant magnetoresistance (GMR) and magnetization of Ag1−xNix−yFey heterogeneous alloy films both experimentally and through computer simulation. The samples were prepared by sputtering from a mosaic target onto glass substrates at the system ambient temperature. They have thicknesses in the range of 100–300 nm and were rapidly thermally annealed at up to 750 °C to promote phase segregation. The resistivity and magnetoresistivity have been measured in the temperature range 4–300 K in fields of up to 12 kOe and the magnetization by vibrating sample magnetometer at fields of up to 6 T. We have modeled the magnetization and GMR of the system using an ensemble of superparamagnetic particles which have a log normal distribution of diameters. We obtain an excellent fit to the experimental magnetization data at room temperature. This is true for all annealing strategies used. Conversely, we have found a marked difference between the modeled and experimental GMR data for higher temperature annealing strategies. It can be shown that this model accurately fits the magnetoresistance if only particles under a critical diameter are considered. For Ag1−xNix−yFey heterogeneous alloy films this critical diameter has been calculated to be 6 nm. Larger particles will contribute only to the magnetization and not the magnetoresistivity. To optimize the magnetoresistance an annealing strategy that favors the creation of particles under this critical diameter is required.

High-birefringent, nematic liquid crystal waveplates, using low-voltage electrical drive signals to provide programmable retardances over several hundred nanometres, have recently become commercially available. Using one of these electro-optic devices for both phase and polarization modulation, we have developed a simple, semi-automatic, null, broadband ellipsometer. This instrument measures the ellipsometric parameters δ and ψ by a technique that does not require measurement of either optical phase or intensity. The operating principle of the ellipsometer is described in detail together with brief details of its construction. Its performance is illustrated by reference to specific optical constant measurements made on a variety of materials including thin films and overcoated magneto-optic recording media.

We have investigated the thickness dependence of the giant magnetoresistance (GMR) observed in AgNiFe heterogeneous alloy films. The films were sputtered from a mosaic target at the system ambient temperature onto glass substrates. In order to maintain interfacial uniformity, and to control the spin-dependent transmission of electrons at the AgNiFe film interfaces, they were covered by 200-Å-thick NiFe under- and overlayers. The samples have total thicknesses in the range 400–3000 Å. The film resistivity, magnetoresistivity, and magnetization were measured in the temperature range 4–300 K and in fields of up to 1.1 T and the structure examined using both large- and small-angle x-ray diffraction. The results indicate that the observed thickness dependence of the GMR of the AgNiFe films is within the experimental error It is postulated that this is due to coherent spin transmission of conduction electrons across the sandwich interfaces which does not degrade the GMR by mixing of the spin currents.

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